shard-crystal-db/api/0.8.0/DB/QueryMethods.html
2019-12-11 17:40:10 -03:00

977 lines
40 KiB
HTML

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="generator" content="Crystal Docs 0.31.1">
<link href="../css/style.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="../js/doc.js"></script>
<svg class="hidden">
<symbol id="octicon-link" viewBox="0 0 16 16">
<path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path>
</symbol>
</svg>
<meta id="repository-name" content="github.com/crystal-lang/crystal-db">
<title>DB::QueryMethods(Stmt) - github.com/crystal-lang/crystal-db</title>
<script type="text/javascript">
CrystalDoc.base_path = "../";
</script>
</head>
<body>
<div class="sidebar">
<div class="sidebar-header">
<div class="search-box">
<input type="search" class="search-input" placeholder="Search..." spellcheck="false" aria-label="Search">
</div>
<div class="repository-links">
<a href="../index.html">README</a>
</div>
</div>
<div class="search-results" class="hidden">
<ul class="search-list"></ul>
</div>
<div class="types-list">
<ul>
<li class="parent open current" data-id="github.com/crystal-lang/crystal-db/DB" data-name="db">
<a href="../DB.html">DB</a>
<ul>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Any" data-name="db::any">
<a href="../DB/Any.html">Any</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/BeginTransaction" data-name="db::begintransaction">
<a href="../DB/BeginTransaction.html">BeginTransaction</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Connection" data-name="db::connection">
<a href="../DB/Connection.html">Connection</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/ConnectionContext" data-name="db::connectioncontext">
<a href="../DB/ConnectionContext.html">ConnectionContext</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/ConnectionLost" data-name="db::connectionlost">
<a href="../DB/ConnectionLost.html">ConnectionLost</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/ConnectionRefused" data-name="db::connectionrefused">
<a href="../DB/ConnectionRefused.html">ConnectionRefused</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Database" data-name="db::database">
<a href="../DB/Database.html">Database</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Disposable" data-name="db::disposable">
<a href="../DB/Disposable.html">Disposable</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Driver" data-name="db::driver">
<a href="../DB/Driver.html">Driver</a>
</li>
<li class="parent " data-id="github.com/crystal-lang/crystal-db/DB/DriverSpecs" data-name="db::driverspecs(dbanytype)">
<a href="../DB/DriverSpecs.html">DriverSpecs</a>
<ul>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/DriverSpecs/ColumnDef" data-name="db::driverspecs::columndef">
<a href="../DB/DriverSpecs/ColumnDef.html">ColumnDef</a>
</li>
</ul>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Error" data-name="db::error">
<a href="../DB/Error.html">Error</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/ExecResult" data-name="db::execresult">
<a href="../DB/ExecResult.html">ExecResult</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Field" data-name="db::field">
<a href="../DB/Field.html">Field</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Mappable" data-name="db::mappable">
<a href="../DB/Mappable.html">Mappable</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/MappingException" data-name="db::mappingexception">
<a href="../DB/MappingException.html">MappingException</a>
</li>
<li class="parent " data-id="github.com/crystal-lang/crystal-db/DB/Pool" data-name="db::pool(t)">
<a href="../DB/Pool.html">Pool</a>
<ul>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Pool/Stats" data-name="db::pool::stats">
<a href="../DB/Pool/Stats.html">Stats</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Pool/TimeoutHelper" data-name="db::pool::timeouthelper">
<a href="../DB/Pool/TimeoutHelper.html">TimeoutHelper</a>
</li>
</ul>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/PoolPreparedStatement" data-name="db::poolpreparedstatement">
<a href="../DB/PoolPreparedStatement.html">PoolPreparedStatement</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/PoolRetryAttemptsExceeded" data-name="db::poolretryattemptsexceeded">
<a href="../DB/PoolRetryAttemptsExceeded.html">PoolRetryAttemptsExceeded</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/PoolStatement" data-name="db::poolstatement">
<a href="../DB/PoolStatement.html">PoolStatement</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/PoolTimeout" data-name="db::pooltimeout">
<a href="../DB/PoolTimeout.html">PoolTimeout</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/PoolUnpreparedStatement" data-name="db::poolunpreparedstatement">
<a href="../DB/PoolUnpreparedStatement.html">PoolUnpreparedStatement</a>
</li>
<li class=" current" data-id="github.com/crystal-lang/crystal-db/DB/QueryMethods" data-name="db::querymethods(stmt)">
<a href="../DB/QueryMethods.html">QueryMethods</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/ResultSet" data-name="db::resultset">
<a href="../DB/ResultSet.html">ResultSet</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Rollback" data-name="db::rollback">
<a href="../DB/Rollback.html">Rollback</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/SavePointTransaction" data-name="db::savepointtransaction">
<a href="../DB/SavePointTransaction.html">SavePointTransaction</a>
</li>
<li class="parent " data-id="github.com/crystal-lang/crystal-db/DB/Serializable" data-name="db::serializable">
<a href="../DB/Serializable.html">Serializable</a>
<ul>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Serializable/NonStrict" data-name="db::serializable::nonstrict">
<a href="../DB/Serializable/NonStrict.html">NonStrict</a>
</li>
</ul>
</li>
<li class="parent " data-id="github.com/crystal-lang/crystal-db/DB/SessionMethods" data-name="db::sessionmethods(session, stmt)">
<a href="../DB/SessionMethods.html">SessionMethods</a>
<ul>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/SessionMethods/PreparedQuery" data-name="db::sessionmethods::preparedquery(session, stmt)">
<a href="../DB/SessionMethods/PreparedQuery.html">PreparedQuery</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/SessionMethods/UnpreparedQuery" data-name="db::sessionmethods::unpreparedquery(session, stmt)">
<a href="../DB/SessionMethods/UnpreparedQuery.html">UnpreparedQuery</a>
</li>
</ul>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Statement" data-name="db::statement">
<a href="../DB/Statement.html">Statement</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/StatementMethods" data-name="db::statementmethods">
<a href="../DB/StatementMethods.html">StatementMethods</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/StringKeyCache" data-name="db::stringkeycache(t)">
<a href="../DB/StringKeyCache.html">StringKeyCache</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/TopLevelTransaction" data-name="db::topleveltransaction">
<a href="../DB/TopLevelTransaction.html">TopLevelTransaction</a>
</li>
<li class=" " data-id="github.com/crystal-lang/crystal-db/DB/Transaction" data-name="db::transaction">
<a href="../DB/Transaction.html">Transaction</a>
</li>
</ul>
</li>
</ul>
</div>
</div>
<div class="main-content">
<h1 class="type-name">
<span class="kind">module</span> DB::QueryMethods(Stmt)
</h1>
<h2>
<a id="overview" class="anchor" href="#overview">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Overview
</h2>
<p>Methods to allow querying a database.
All methods accepts a <code>query : String</code> and a set arguments.</p>
<p>Three kind of statements can be performed:</p>
<ol><li><code><a href="../DB/QueryMethods.html#exec(query,*args_,args:Array?=nil)-instance-method">#exec</a></code> waits no record response from the database. An <code><a href="../DB/ExecResult.html">ExecResult</a></code> is returned.</li><li><code><a href="../DB/QueryMethods.html#scalar(query,*args_,args:Array?=nil)-instance-method">#scalar</a></code> reads a single value of the response. A union of possible values is returned.</li><li><code><a href="../DB/QueryMethods.html#query(query,*args_,args:Array?=nil)-instance-method">#query</a></code> returns a <code><a href="../DB/ResultSet.html">ResultSet</a></code> that allows iteration over the rows in the response and column information.</li></ol>
<p>Arguments can be passed by position or as an array.</p>
<pre><code>db.query(<span class="s">&quot;SELECT name FROM ... WHERE age &gt; ?&quot;</span>, age)
db.query(<span class="s">&quot;SELECT name FROM ... WHERE age &gt; ?&quot;</span>, args: [age])</code></pre>
<p>Convention of mapping how arguments are mapped to the query depends on each driver.</p>
<p>Including <code><a href="../DB/QueryMethods.html">QueryMethods</a></code> requires a <code>build(query) : <a href="../DB/Statement.html">Statement</a></code> method that is not expected
to be called directly.</p>
<h2>
<a id="direct-including-types" class="anchor" href="#direct-including-types">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Direct including types
</h2>
<ul class="other-types-list">
<li class="other-type"><a href="../DB/SessionMethods.html">DB::SessionMethods(Session, Stmt)</a></li>
<li class="other-type"><a href="../DB/SessionMethods/PreparedQuery.html">DB::SessionMethods::PreparedQuery(Session, Stmt)</a></li>
<li class="other-type"><a href="../DB/SessionMethods/UnpreparedQuery.html">DB::SessionMethods::UnpreparedQuery(Session, Stmt)</a></li>
</ul>
<h2>
<a id="defined-in" class="anchor" href="#defined-in">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Defined in:
</h2>
<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L21" target="_blank">
db/query_methods.cr
</a>
<br/>
<h2>
<a id="instance-method-summary" class="anchor" href="#instance-method-summary">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Instance Method Summary
</h2>
<ul class="list-summary">
<li class="entry-summary">
<a href="#exec(query,*args_,args:Array?=nil)-instance-method" class="signature"><strong>#exec</strong>(query, *args_, args : Array? = <span class="n">nil</span>)</a>
<div class="summary"><p>Performs the <code><a href="../DB/QueryMethods.html#query(query,*args_,args:Array?=nil)-instance-method">#query</a></code> and returns an <code><a href="../DB/ExecResult.html">ExecResult</a></code></p></div>
</li>
<li class="entry-summary">
<a href="#query(query,*args_,args:Array?=nil)-instance-method" class="signature"><strong>#query</strong>(query, *args_, args : Array? = <span class="n">nil</span>)</a>
<div class="summary"><p>Executes a <em>query</em> and returns a <code><a href="../DB/ResultSet.html">ResultSet</a></code> with the results.</p></div>
</li>
<li class="entry-summary">
<a href="#query(query,*args_,args:Array?=nil,&)-instance-method" class="signature"><strong>#query</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &)</a>
<div class="summary"><p>Executes a <em>query</em> and yields a <code><a href="../DB/ResultSet.html">ResultSet</a></code> with the results.</p></div>
</li>
<li class="entry-summary">
<a href="#query_all(query,*args_,args:Array?=nil,astype:Class)-instance-method" class="signature"><strong>#query_all</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as type : Class)</a>
<div class="summary"><p>Executes a <em>query</em> and returns an array where the value of each row is read as the given <em>type</em>.</p></div>
</li>
<li class="entry-summary">
<a href="#query_all(query,*args_,args:Array?=nil,astypes:NamedTuple)-instance-method" class="signature"><strong>#query_all</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : NamedTuple)</a>
<div class="summary"><p>Executes a <em>query</em> and returns an array where each row is read as a named tuple of the given <em>types</em> (the keys of the named tuple are not necessarily the column names).</p></div>
</li>
<li class="entry-summary">
<a href="#query_all(query,*args_,args:Array?=nil,&block:ResultSet-%3EU):Array(U)forallU-instance-method" class="signature"><strong>#query_all</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &block : ResultSet -> U) : Array(U) forall U</a>
<div class="summary"><p>Executes a <em>query</em> and yield a <code><a href="../DB/ResultSet.html">ResultSet</a></code> positioned at the beginning of each row, returning an array of the values of the blocks.</p></div>
</li>
<li class="entry-summary">
<a href="#query_all(query,*args_,args:Array?=nil,astypes:Tuple)-instance-method" class="signature"><strong>#query_all</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : Tuple)</a>
<div class="summary"><p>Executes a <em>query</em> and returns an array where each row is read as a tuple of the given <em>types</em>.</p></div>
</li>
<li class="entry-summary">
<a href="#query_each(query,*args_,args:Array?=nil,&)-instance-method" class="signature"><strong>#query_each</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &)</a>
<div class="summary"><p>Executes a <em>query</em> and yields the <code><a href="../DB/ResultSet.html">ResultSet</a></code> once per each row.</p></div>
</li>
<li class="entry-summary">
<a href="#query_one(query,*args_,args:Array?=nil,&block:ResultSet-%3EU):UforallU-instance-method" class="signature"><strong>#query_one</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &block : ResultSet -> U) : U forall U</a>
<div class="summary"><p>Executes a <em>query</em> that expects a single row and yields a <code><a href="../DB/ResultSet.html">ResultSet</a></code> positioned at that first row.</p></div>
</li>
<li class="entry-summary">
<a href="#query_one(query,*args_,args:Array?=nil,astypes:Tuple)-instance-method" class="signature"><strong>#query_one</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : Tuple)</a>
<div class="summary"><p>Executes a <em>query</em> that expects a single row and returns it as a tuple of the given <em>types</em>.</p></div>
</li>
<li class="entry-summary">
<a href="#query_one(query,*args_,args:Array?=nil,astypes:NamedTuple)-instance-method" class="signature"><strong>#query_one</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : NamedTuple)</a>
<div class="summary"><p>Executes a <em>query</em> that expects a single row and returns it as a named tuple of the given <em>types</em> (the keys of the named tuple are not necessarily the column names).</p></div>
</li>
<li class="entry-summary">
<a href="#query_one(query,*args_,args:Array?=nil,astype:Class)-instance-method" class="signature"><strong>#query_one</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as type : Class)</a>
<div class="summary"><p>Executes a <em>query</em> that expects a single row and returns the first column's value as the given <em>type</em>.</p></div>
</li>
<li class="entry-summary">
<a href="#query_one?(query,*args_,args:Array?=nil,astype:Class)-instance-method" class="signature"><strong>#query_one?</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as type : Class)</a>
<div class="summary"><p>Executes a <em>query</em> that expects a single row and returns the first column's value as the given <em>type</em>.</p></div>
</li>
<li class="entry-summary">
<a href="#query_one?(query,*args_,args:Array?=nil,astypes:NamedTuple)-instance-method" class="signature"><strong>#query_one?</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : NamedTuple)</a>
<div class="summary"><p>Executes a <em>query</em> that expects a single row and returns it as a named tuple of the given <em>types</em> (the keys of the named tuple are not necessarily the column names).</p></div>
</li>
<li class="entry-summary">
<a href="#query_one?(query,*args_,args:Array?=nil,astypes:Tuple)-instance-method" class="signature"><strong>#query_one?</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : Tuple)</a>
<div class="summary"><p>Executes a <em>query</em> that expects a single row and returns it as a tuple of the given <em>types</em>.</p></div>
</li>
<li class="entry-summary">
<a href="#query_one?(query,*args_,args:Array?=nil,&block:ResultSet-%3EU):U?forallU-instance-method" class="signature"><strong>#query_one?</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &block : ResultSet -> U) : U? forall U</a>
<div class="summary"><p>Executes a <em>query</em> that expects at most a single row and yields a <code><a href="../DB/ResultSet.html">ResultSet</a></code> positioned at that first row.</p></div>
</li>
<li class="entry-summary">
<a href="#scalar(query,*args_,args:Array?=nil)-instance-method" class="signature"><strong>#scalar</strong>(query, *args_, args : Array? = <span class="n">nil</span>)</a>
<div class="summary"><p>Performs the <code><a href="../DB/QueryMethods.html#query(query,*args_,args:Array?=nil)-instance-method">#query</a></code> and returns a single scalar value</p></div>
</li>
</ul>
<div class="methods-inherited">
</div>
<h2>
<a id="instance-method-detail" class="anchor" href="#instance-method-detail">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Instance Method Detail
</h2>
<div class="entry-detail" id="exec(query,*args_,args:Array?=nil)-instance-method">
<div class="signature">
def <strong>exec</strong>(query, *args_, args : Array? = <span class="n">nil</span>)
<a class="method-permalink" href="#exec(query,*args_,args:Array?=nil)-instance-method">#</a>
</div>
<div class="doc">
<p>Performs the <code><a href="../DB/QueryMethods.html#query(query,*args_,args:Array?=nil)-instance-method">#query</a></code> and returns an <code><a href="../DB/ExecResult.html">ExecResult</a></code></p>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L270" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query(query,*args_,args:Array?=nil)-instance-method">
<div class="signature">
def <strong>query</strong>(query, *args_, args : Array? = <span class="n">nil</span>)
<a class="method-permalink" href="#query(query,*args_,args:Array?=nil)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> and returns a <code><a href="../DB/ResultSet.html">ResultSet</a></code> with the results.
The <code><a href="../DB/ResultSet.html">ResultSet</a></code> must be closed manually.</p>
<pre><code>result <span class="o">=</span> db.query <span class="s">&quot;select name from contacts where id = ?&quot;</span>, <span class="n">10</span>
<span class="k">begin</span>
<span class="k">if</span> result.move_next
id <span class="o">=</span> result.read(<span class="t">Int32</span>)
<span class="k">end</span>
<span class="k">ensure</span>
result.close
<span class="k">end</span></code></pre>
<p>Note: to use a dynamic list length of arguments use <code>args:</code> keyword argument.</p>
<pre><code>result <span class="o">=</span> db.query <span class="s">&quot;select name from contacts where id = ?&quot;</span>, args: [<span class="n">10</span>]</code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L45" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query(query,*args_,args:Array?=nil,&amp;)-instance-method">
<div class="signature">
def <strong>query</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &)
<a class="method-permalink" href="#query(query,*args_,args:Array?=nil,&)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> and yields a <code><a href="../DB/ResultSet.html">ResultSet</a></code> with the results.
The <code><a href="../DB/ResultSet.html">ResultSet</a></code> is closed automatically.</p>
<pre><code>db.query(<span class="s">&quot;select name from contacts where age &gt; ?&quot;</span>, <span class="n">18</span>) <span class="k">do</span> <span class="o">|</span>rs<span class="o">|</span>
rs.each <span class="k">do</span>
name <span class="o">=</span> rs.read(<span class="t">String</span>)
<span class="k">end</span>
<span class="k">end</span></code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L59" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_all(query,*args_,args:Array?=nil,astype:Class)-instance-method">
<div class="signature">
def <strong>query_all</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as type : Class)
<a class="method-permalink" href="#query_all(query,*args_,args:Array?=nil,astype:Class)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> and returns an array where the
value of each row is read as the given <em>type</em>.</p>
<pre><code>names <span class="o">=</span> db.query_all <span class="s">&quot;select name from contacts&quot;</span>, <span class="k">as</span>: <span class="t">String</span></code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L247" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_all(query,*args_,args:Array?=nil,astypes:NamedTuple)-instance-method">
<div class="signature">
def <strong>query_all</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : NamedTuple)
<a class="method-permalink" href="#query_all(query,*args_,args:Array?=nil,astypes:NamedTuple)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> and returns an array where each row is
read as a named tuple of the given <em>types</em> (the keys of the named tuple
are not necessarily the column names).</p>
<pre><code>contacts <span class="o">=</span> db.query_all <span class="s">&quot;select name, age from contacts&quot;</span>, <span class="k">as</span>: {name: <span class="t">String</span>, age: <span class="t">Int32</span>}</code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L235" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_all(query,*args_,args:Array?=nil,&amp;block:ResultSet-&gt;U):Array(U)forallU-instance-method">
<div class="signature">
def <strong>query_all</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &block : <a href="../DB/ResultSet.html">ResultSet</a> -> U) : Array(U) forall U
<a class="method-permalink" href="#query_all(query,*args_,args:Array?=nil,&block:ResultSet-%3EU):Array(U)forallU-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> and yield a <code><a href="../DB/ResultSet.html">ResultSet</a></code> positioned at the beginning
of each row, returning an array of the values of the blocks.</p>
<pre><code>names <span class="o">=</span> db.query_all <span class="s">&quot;select name from contacts&quot;</span>, <span class="o">&amp;</span>.read(<span class="t">String</span>)</code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L208" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_all(query,*args_,args:Array?=nil,astypes:Tuple)-instance-method">
<div class="signature">
def <strong>query_all</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : Tuple)
<a class="method-permalink" href="#query_all(query,*args_,args:Array?=nil,astypes:Tuple)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> and returns an array where each row is
read as a tuple of the given <em>types</em>.</p>
<pre><code>contacts <span class="o">=</span> db.query_all <span class="s">&quot;select name, age from contacts&quot;</span>, <span class="k">as</span>: {<span class="t">String</span>, <span class="t">Int32</span>}</code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L222" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_each(query,*args_,args:Array?=nil,&amp;)-instance-method">
<div class="signature">
def <strong>query_each</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &)
<a class="method-permalink" href="#query_each(query,*args_,args:Array?=nil,&)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> and yields the <code><a href="../DB/ResultSet.html">ResultSet</a></code> once per each row.
The <code><a href="../DB/ResultSet.html">ResultSet</a></code> is closed automatically.</p>
<pre><code>db.query_each <span class="s">&quot;select name from contacts&quot;</span> <span class="k">do</span> <span class="o">|</span>rs<span class="o">|</span>
puts rs.read(<span class="t">String</span>)
<span class="k">end</span></code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L261" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_one(query,*args_,args:Array?=nil,&amp;block:ResultSet-&gt;U):UforallU-instance-method">
<div class="signature">
def <strong>query_one</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &block : <a href="../DB/ResultSet.html">ResultSet</a> -> U) : U forall U
<a class="method-permalink" href="#query_one(query,*args_,args:Array?=nil,&block:ResultSet-%3EU):UforallU-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> that expects a single row and yields a <code><a href="../DB/ResultSet.html">ResultSet</a></code>
positioned at that first row.</p>
<p>The given block must not invoke <code>move_next</code> on the yielded result set.</p>
<p>Raises <code><a href="../DB/Error.html">DB::Error</a></code> if there were no rows, or if there were more than one row.</p>
<pre><code>name <span class="o">=</span> db.query_one <span class="s">&quot;select name from contacts where id = ?&quot;</span>, <span class="n">18</span>, <span class="o">&amp;</span>.read(<span class="t">String</span>)</code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L75" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_one(query,*args_,args:Array?=nil,astypes:Tuple)-instance-method">
<div class="signature">
def <strong>query_one</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : Tuple)
<a class="method-permalink" href="#query_one(query,*args_,args:Array?=nil,astypes:Tuple)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> that expects a single row and returns it
as a tuple of the given <em>types</em>.</p>
<p>Raises <code><a href="../DB/Error.html">DB::Error</a></code> if there were no rows, or if there were more than one row.</p>
<pre><code>db.query_one <span class="s">&quot;select name, age from contacts where id = ?&quot;</span>, <span class="n">1</span>, <span class="k">as</span>: {<span class="t">String</span>, <span class="t">Int32</span>}</code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L93" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_one(query,*args_,args:Array?=nil,astypes:NamedTuple)-instance-method">
<div class="signature">
def <strong>query_one</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : NamedTuple)
<a class="method-permalink" href="#query_one(query,*args_,args:Array?=nil,astypes:NamedTuple)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> that expects a single row and returns it
as a named tuple of the given <em>types</em> (the keys of the named tuple
are not necessarily the column names).</p>
<p>Raises <code><a href="../DB/Error.html">DB::Error</a></code> if there were no rows, or if there were more than one row.</p>
<pre><code>db.query_one <span class="s">&quot;select name, age from contacts where id = ?&quot;</span>, <span class="n">1</span>, <span class="k">as</span>: {name: <span class="t">String</span>, age: <span class="t">Int32</span>}</code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L108" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_one(query,*args_,args:Array?=nil,astype:Class)-instance-method">
<div class="signature">
def <strong>query_one</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as type : Class)
<a class="method-permalink" href="#query_one(query,*args_,args:Array?=nil,astype:Class)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> that expects a single row
and returns the first column's value as the given <em>type</em>.</p>
<p>Raises <code><a href="../DB/Error.html">DB::Error</a></code> if there were no rows, or if there were more than one row.</p>
<pre><code>db.query_one <span class="s">&quot;select name from contacts where id = ?&quot;</span>, <span class="n">1</span>, <span class="k">as</span>: <span class="t">String</span></code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L122" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_one?(query,*args_,args:Array?=nil,astype:Class)-instance-method">
<div class="signature">
def <strong>query_one?</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as type : Class)
<a class="method-permalink" href="#query_one?(query,*args_,args:Array?=nil,astype:Class)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> that expects a single row
and returns the first column's value as the given <em>type</em>.</p>
<p>Returns <code>nil</code> if there were no rows.</p>
<p>Raises <code><a href="../DB/Error.html">DB::Error</a></code> if there were more than one row.</p>
<pre><code>name <span class="o">=</span> db.query_one? <span class="s">&quot;select name from contacts where id = ?&quot;</span>, <span class="n">1</span>, <span class="k">as</span>: <span class="t">String</span>
<span class="k">typeof</span>(name) <span class="c"># =&gt; String?</span></code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L196" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_one?(query,*args_,args:Array?=nil,astypes:NamedTuple)-instance-method">
<div class="signature">
def <strong>query_one?</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : NamedTuple)
<a class="method-permalink" href="#query_one?(query,*args_,args:Array?=nil,astypes:NamedTuple)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> that expects a single row and returns it
as a named tuple of the given <em>types</em> (the keys of the named tuple
are not necessarily the column names).</p>
<p>Returns <code>nil</code> if there were no rows.</p>
<p>Raises <code><a href="../DB/Error.html">DB::Error</a></code> if there were more than one row.</p>
<pre><code>result <span class="o">=</span> db.query_one? <span class="s">&quot;select name, age from contacts where id = ?&quot;</span>, <span class="n">1</span>, <span class="k">as</span>: {age: <span class="t">String</span>, name: <span class="t">Int32</span>}
<span class="k">typeof</span>(result) <span class="c"># =&gt; NamedTuple(age: String, name: Int32) | Nil</span></code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L179" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_one?(query,*args_,args:Array?=nil,astypes:Tuple)-instance-method">
<div class="signature">
def <strong>query_one?</strong>(query, *args_, args : Array? = <span class="n">nil</span>, as types : Tuple)
<a class="method-permalink" href="#query_one?(query,*args_,args:Array?=nil,astypes:Tuple)-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> that expects a single row and returns it
as a tuple of the given <em>types</em>.</p>
<p>Returns <code>nil</code> if there were no rows.</p>
<p>Raises <code><a href="../DB/Error.html">DB::Error</a></code> if there were more than one row.</p>
<pre><code>result <span class="o">=</span> db.query_one? <span class="s">&quot;select name, age from contacts where id = ?&quot;</span>, <span class="n">1</span>, <span class="k">as</span>: {<span class="t">String</span>, <span class="t">Int32</span>}
<span class="k">typeof</span>(result) <span class="c"># =&gt; Tuple(String, Int32) | Nil</span></code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L161" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="query_one?(query,*args_,args:Array?=nil,&amp;block:ResultSet-&gt;U):U?forallU-instance-method">
<div class="signature">
def <strong>query_one?</strong>(query, *args_, args : Array? = <span class="n">nil</span>, &block : <a href="../DB/ResultSet.html">ResultSet</a> -> U) : U? forall U
<a class="method-permalink" href="#query_one?(query,*args_,args:Array?=nil,&block:ResultSet-%3EU):U?forallU-instance-method">#</a>
</div>
<div class="doc">
<p>Executes a <em>query</em> that expects at most a single row and yields a <code><a href="../DB/ResultSet.html">ResultSet</a></code>
positioned at that first row.</p>
<p>Returns <code>nil</code>, not invoking the block, if there were no rows.</p>
<p>Raises <code><a href="../DB/Error.html">DB::Error</a></code> if there were more than one row
(this ends up invoking the block once).</p>
<pre><code>name <span class="o">=</span> db.query_one? <span class="s">&quot;select name from contacts where id = ?&quot;</span>, <span class="n">18</span>, <span class="o">&amp;</span>.read(<span class="t">String</span>)
<span class="k">typeof</span>(name) <span class="c"># =&gt; String | Nil</span></code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L140" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="scalar(query,*args_,args:Array?=nil)-instance-method">
<div class="signature">
def <strong>scalar</strong>(query, *args_, args : Array? = <span class="n">nil</span>)
<a class="method-permalink" href="#scalar(query,*args_,args:Array?=nil)-instance-method">#</a>
</div>
<div class="doc">
<p>Performs the <code><a href="../DB/QueryMethods.html#query(query,*args_,args:Array?=nil)-instance-method">#query</a></code> and returns a single scalar value</p>
<pre><code>puts db.scalar(<span class="s">&quot;SELECT MAX(name)&quot;</span>).<span class="k">as</span>(<span class="t">String</span>) <span class="c"># =&gt; (a String)</span></code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/7e83f8e26c2f9a5cde0693007b1c1486d00f7685/src/db/query_methods.cr#L279" target="_blank">View source</a>]
</div>
</div>
</div>
</body>
</html>