Documentation

Query extends Query
in package

Query represents a SELECT SQL statement in a way that is independent of DBMS.

Query provides a set of methods to facilitate the specification of different clauses in a SELECT statement. These methods can be chained together.

By calling [[createCommand()]], we can get a [[Command]] instance which can be further used to perform/execute the DB query against a database.

Table of Contents

batch()  : BatchQueryResult
Starts a batch query.
createCommand()  : Command
Creates a DB command that can be used to execute this query.
each()  : BatchQueryResult
Starts a batch query and retrieves data row by row.
one()  : array<string|int, mixed>|bool
Executes the query and returns a single row of result.
scalar()  : string|false|null
Returns the query result as a scalar value.
queryScalar()  : bool|string
Queries a scalar value by setting [[select]] first.

Methods

batch()

Starts a batch query.

public batch([int $batchSize = 100 ][, Db $db = null ]) : BatchQueryResult

A batch query supports fetching data in batches, which can keep the memory usage under a limit. This method will return a [[BatchQueryResult]] object which implements the [[\Iterator]] interface and can be traversed to retrieve the data in batches.

Parameters
$batchSize : int = 100

the number of records to be fetched in each batch.

$db : Db = null

the database connection. If not set, the "db" application component will be used.

Return values
BatchQueryResult —

the batch query result. It implements the [[\Iterator]] interface and can be traversed to retrieve the data in batches.

createCommand()

Creates a DB command that can be used to execute this query.

public createCommand([Db $db = null ]) : Command
Parameters
$db : Db = null

the database connection used to generate the SQL statement. If this parameter is not given, the db application component will be used.

Return values
Command —

the created DB command instance.

each()

Starts a batch query and retrieves data row by row.

public each([int $batchSize = 100 ][, Db $db = null ]) : BatchQueryResult

This method is similar to [[batch()]] except that in each iteration of the result, only one row of data is returned. For example,

Parameters
$batchSize : int = 100

the number of records to be fetched in each batch.

$db : Db = null

the database connection. If not set, the "db" application component will be used.

Return values
BatchQueryResult —

the batch query result. It implements the [[\Iterator]] interface and can be traversed to retrieve the data in batches.

one()

Executes the query and returns a single row of result.

public one([Db $db = null ]) : array<string|int, mixed>|bool
Parameters
$db : Db = null

the database connection used to generate the SQL statement. If this parameter is not given, the db application component will be used.

Return values
array<string|int, mixed>|bool —

the first row (in terms of an array) of the query result. False is returned if the query results in nothing.

scalar()

Returns the query result as a scalar value.

public scalar([Db $db = null ]) : string|false|null

The value returned will be the first column in the first row of the query results.

Parameters
$db : Db = null

the database connection used to generate the SQL statement. If this parameter is not given, the db application component will be used.

Return values
string|false|null —

the value of the first column in the first row of the query result. False is returned if the query result is empty.

queryScalar()

Queries a scalar value by setting [[select]] first.

protected queryScalar(string|ExpressionInterface $selectExpression, Db|null $db) : bool|string

Restores the value of select to make this query reusable.

Parameters
$selectExpression : string|ExpressionInterface
$db : Db|null
Return values
bool|string — 

        

        
    




    

    

                

    

        

            
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