yii2-bootstrap/docs/guide/query-builder.md

Query Builder and Query

Yii provides a basic database access layer as was described in Database basics section. Still it's a bit too much to use SQL directly all the time. To solve the issue Yii provides a query builder that allows you to work with the database in object-oriented style.

Basic query builder usage is the following:

$query = new Query;

// Define query
$query->select('id, name')
 	->from('tbl_user')
 	->limit(10);

// Create a command. You can get the actual SQL using $command->sql
$command = $query->createCommand();
// Execute command
$rows = $command->queryAll();

Basic selects and joins

In order to form a SELECT query you need to specify what to select and where to select it from.

$query->select('id, name')
	->from('tbl_user');

If you want to get IDs of all users with posts you can use DISTINCT. With query builder it will look like the following:

$query->select('user_id')->distinct()->from('tbl_post');

Select options can be specified as array. It's especially useful when these are formed dynamically.

$query->select(array('tbl_user.name AS author', 'tbl_post.title as title')) // <-- specified as array
	->from('tbl_user')
	->leftJoin('tbl_post', 'tbl_post.user_id = tbl_user.id'); // <-- join with another table

In the code above we've used leftJoin method to select from two related tables at the same time. Firsrt parameter specifies table name and the second is the join condition. Query builder has the following methods to join tables:

• innerJoin
• leftJoin
• rightJoin

If your data storage supports more types you can use generic join method:

$query->join('FULL OUTER JOIN', 'tbl_post', 'tbl_post.user_id = tbl_user.id');

Specifying conditions

Usually you need data that matches some conditions. There are some useful methods to specify these and the most powerful is where. There are multiple ways to use it.

The simplest is to specify condition in a string:

$query->where('status=:status', array(
	':status' => $status,
));

When using this format make sure you're binding parameters and not creating a query by string concatenation.

Instead of binding status value immediately you can do it using params or addParams:

$query->where('status=:status');

$query->addParams(array(
	':status' => $status,
));

There is another convenient way to use the method called hash format:

$query->where(array(
	'status' => 10,
	'type' => 2,
	'id' => array(4, 8, 15, 16, 23, 42),
));

It will generate the following SQL:

WHERE (`status` = 10) AND (`type` = 2) AND (`id` IN (4, 8, 15, 16, 23, 42))

If you'll specify value as null such as the following:

$query->where(array(
	'status' => null,
));

SQL generated will be:

WHERE (`status` IS NULL)

Another way to use the method is the operand format which is array(operator, operand1, operand2, ...).

Operator can be one of the following:

• and: the operands should be concatenated together using AND. For example, array('and', 'id=1', 'id=2') will generate id=1 AND id=2. If an operand is an array, it will be converted into a string using the rules described here. For example, array('and', 'type=1', array('or', 'id=1', 'id=2')) will generate type=1 AND (id=1 OR id=2). The method will NOT do any quoting or escaping.
• or: similar to the and operator except that the operands are concatenated using OR.
• between: operand 1 should be the column name, and operand 2 and 3 should be the starting and ending values of the range that the column is in. For example, array('between', 'id', 1, 10) will generate id BETWEEN 1 AND 10.
• not between: similar to between except the BETWEEN is replaced with NOT BETWEEN in the generated condition.
• in: operand 1 should be a column or DB expression, and operand 2 be an array representing the range of the values that the column or DB expression should be in. For example, array('in', 'id', array(1, 2, 3)) will generate id IN (1, 2, 3). The method will properly quote the column name and escape values in the range.
• not in: similar to the in operator except that IN is replaced with NOT IN in the generated condition.
• like: operand 1 should be a column or DB expression, and operand 2 be a string or an array representing the values that the column or DB expression should be like. For example, array('like', 'name', '%tester%') will generate name LIKE '%tester%'. When the value range is given as an array, multiple LIKE predicates will be generated and concatenated using AND. For example, array('like', 'name', array('%test%', '%sample%')) will generate name LIKE '%test%' AND name LIKE '%sample%'. The method will properly quote the column name and escape values in the range.
• or like: similar to the like operator except that OR is used to concatenate the LIKE predicates when operand 2 is an array.
• not like: similar to the like operator except that LIKE is replaced with NOT LIKE in the generated condition.
• or not like: similar to the not like operator except that OR is used to concatenate the NOT LIKE predicates.

If you are building parts of condition dynamically it's very convenient to use andWhere and orWhere:

$status = 10;
$search = 'yii';

$query->where(array('status' => $status));
if (!empty($search)) {
	$query->addWhere('like', 'title', $search);
}

In case $search isn't empty the following SQL will be generated:

WHERE (`status` = 10) AND (`title` LIKE '%yii%')

Order

For odering results orderBy and addOrderBy could be used:

$query->orderBy(array(
	'id' => Query::SORT_ASC,
	'name' => Query::SORT_DESC,
));

Here we are ordering by id ascending and then by name descending.

Group and Having

In order to add GROUP BY to generated SQL you can use the following:

$query->groupBy('id, status');

If you want to add another field after using groupBy:

$query->addGroupBy(array('created_at', 'updated_at'));

To add a HAVING condition the corresponding having method and its andHaving and orHaving can be used. Parameters for these are similar to the ones for where methods group:

$query->having(array('status' => $status));

Limit and offset

To limit result to 10 rows limit can be used:

$query->limit(10);

To skip 100 fist rows use:

$query->offset(100);

Union

UNION in SQL adds results of one query to results of another query. Columns returned by both queries should match. In Yii in order to build it you can first form two query objects and then use union method:

$query = new Query;
$query->select("id, 'post' as type, name")->from('tbl_post')->limit(10);

$anotherQuery = new Query;
$query->select('id, 'user' as type, name')->from('tbl_user')->limit(10);

$query->union($anotherQuery);