Yii学习（九）数据库 Query Builder 上

1.建立数据库连接

$connection=new CDbConnection($dsn,$username,$password);
// 建立连接。你可以使用  try...catch 捕获可能抛出的异常
$connection->active=true;
......
$connection->active=false;  // 关闭连接

2.示范：

$user = Yii::app()->db->createCommand()
->select('id, username, profile')
->from('tbl_user u')
->join('tbl_profile p', 'u.id=p.user_id')
->where('id=:id', array(':id'=>$id))
->queryRow();

3.连贯操作

$command = Yii::app()->db->createCommand('SELECT * FROM tbl_user');
// the following line will NOT append WHERE clause to the above SQL
$command->where('id=:id', array(':id'=>$id));

Just beginning！

1.准备

$command = Yii::app()->db->createCommand();

2.方法

select(): specifies the SELECT part of the query
selectDistinct(): specifies the SELECT part of the query and turns on the DISTINCT flag
from(): specifies the FROM part of the query
where(): specifies the WHERE part of the query
join(): appends an inner join query fragment
leftJoin(): appends a left outer join query fragment
rightJoin(): appends a right outer join query fragment
crossJoin(): appends a cross join query fragment
naturalJoin(): appends a natural join query fragment
group(): specifies the GROUP BY part of the query
having(): specifies the HAVING part of the query
order(): specifies the ORDER BY part of the query
limit(): specifies the LIMIT part of the query
offset(): specifies the OFFSET part of the query
union(): appends a UNION query fragment

select():

function select($columns='*')
// SELECT *
select()
// SELECT `id`, `username`
select('id, username')
// SELECT `tbl_user`.`id`, `username` AS `name`
select('tbl_user.id, username as name')
// SELECT `id`, `username`
select(array('id', 'username'))
// SELECT `id`, count(*) as num
select(array('id', 'count(*) as num'))

selectDistinct():

function selectDistinct($columns)

selectDistinct('id, username') => SELECT DISTINCT `id`, `username`

from():

function from($tables)
// FROM `tbl_user`
from('tbl_user')
// FROM `tbl_user` `u`, `public`.`tbl_profile` `p`
from('tbl_user u, public.tbl_profile p')
// FROM `tbl_user`, `tbl_profile`
from(array('tbl_user', 'tbl_profile'))
// FROM `tbl_user`, (select * from tbl_profile) p
from(array('tbl_user', '(select * from tbl_profile) p'))

where():

function where($conditions, $params=array())
array(operator, operand1, operand2, ...)

// WHERE id=1 or id=2
where('id=1 or id=2')
// WHERE id=:id1 or id=:id2
where('id=:id1 or id=:id2', array(':id1'=>1, ':id2'=>2))
// WHERE id=1 OR id=2
where(array('or', 'id=1', 'id=2'))
// WHERE id=1 AND (type=2 OR type=3)
where(array('and', 'id=1', array('or', 'type=2', 'type=3')))
// WHERE `id` IN (1, 2)
where(array('in', 'id', array(1, 2))
// WHERE `id` NOT IN (1, 2)
where(array('not in', 'id', array(1,2)))
// WHERE `name` LIKE '%Qiang%'
where(array('like', 'name', '%Qiang%'))
// WHERE `name` LIKE '%Qiang' AND `name` LIKE '%Xue'
where(array('like', 'name', array('%Qiang', '%Xue')))
// WHERE `name` LIKE '%Qiang' OR `name` LIKE '%Xue'
where(array('or like', 'name', array('%Qiang', '%Xue')))
// WHERE `name` NOT LIKE '%Qiang%'
where(array('not like', 'name', '%Qiang%'))
// WHERE `name` NOT LIKE '%Qiang%' OR `name` NOT LIKE '%Xue%'
where(array('or not like', 'name', array('%Qiang%', '%Xue%')))

$keyword=$_GET['q'];
// escape % and _ characters
$keyword=strtr($keyword, array('%'=>'\%', '_'=>'\_'));
$command->where(array('like', 'title', '%'.$keyword.'%'));

order():

function order($columns)

// ORDER BY `name`, `id` DESC
order('name, id desc')
// ORDER BY `tbl_profile`.`name`, `id` DESC
order(array('tbl_profile.name', 'id desc'))

limit() and offset():

function limit($limit, $offset=null)
function offset($offset)

// LIMIT 10
limit(10)
// LIMIT 10 OFFSET 20
limit(10, 20)
// OFFSET 20
offset(20)

join() and its variants:

function join($table, $conditions, $params=array())
function leftJoin($table, $conditions, $params=array())
function rightJoin($table, $conditions, $params=array())
function crossJoin($table)
function naturalJoin($table)

// JOIN `tbl_profile` ON user_id=id
join('tbl_profile', 'user_id=id')
// LEFT JOIN `pub`.`tbl_profile` `p` ON p.user_id=id AND type=1
leftJoin('pub.tbl_profile p', 'p.user_id=id AND type=:type', array(':type'=>1))

group():

function group($columns)

// GROUP BY `name`, `id`
group('name, id')
// GROUP BY `tbl_profile`.`name`, `id`
group(array('tbl_profile.name', 'id'))

having():

function having($conditions, $params=array())

// HAVING id=1 or id=2
having('id=1 or id=2')
// HAVING id=1 OR id=2
having(array('or', 'id=1', 'id=2'))

union():

function union($sql)

// UNION (select * from tbl_profile)
union('select * from tbl_profile')

3.执行

$users = Yii::app()->db->createCommand()
->select('*')
->from('tbl_user')
->queryAll();

返回sql语句

$sql = Yii::app()->db->createCommand()
->select('*')
->from('tbl_user')
->text;

等效

$command->select(array('id', 'username'));
$command->select = array('id', 'username');

绑定

$row = Yii::app()->db->createCommand(array(
'select' => array('id', 'username'),
'from' => 'tbl_user',
'where' => 'id=:id',
'params' => array(':id'=>1),
))->queryRow();

清理上一次操作

$command = Yii::app()->db->createCommand();
$users = $command->select('*')->from('tbl_users')->queryAll();
$command->reset();  // clean up the previous query
$posts = $command->select('*')->from('tbl_posts')->queryAll();

insert()：

function insert($table, $columns)

// build and execute the following SQL:
// INSERT INTO `tbl_user` (`name`, `email`) VALUES (:name, :email)
$command->insert('tbl_user', array(
'name'=>'Tester',
'email'=>'tester@example.com',
));

update()：

function update($table, $columns, $conditions='', $params=array())

// build and execute the following SQL:
// UPDATE `tbl_user` SET `name`=:name WHERE id=:id
$command->update('tbl_user', array(
'name'=>'Tester',
), 'id=:id', array(':id'=>1));

delete()：

function delete($table, $conditions='', $params=array())

// build and execute the following SQL:
// DELETE FROM `tbl_user` WHERE id=:id
$command->delete('tbl_user', 'id=:id', array(':id'=>1));