sql中or语法介绍

  $sql = 'SELECT 
                * 
            FROM 
                `vvt_spread_doubleegg_exchange_award` AS p
            WHERE
                p.`act_type` = 4 or p.`act_type` = 5
            AND
                p.`user_id` = ' .$user_id
            ;

sql中的or语法一般用于多个条件的查询，上面的语法查询的相当于：两个sql查询出来的数据集合。

  $sql = 'SELECT *  FROM  `vvt_spread_doubleegg_exchange_award` AS p WHERE  p.`act_type` = 4;
$sql = 'SELECT * FROM `vvt_spread_doubleegg_exchange_award` AS p WHERE  p.`act_type` = 5 AND p.`user_id` = ' .$user_id;

2. 要想查询act_type = 4 and user_id = 11123 或者等于 p.`act_type` = 5 and user_id = 11123的数据集合 or两边的条件一定要加（）。

  $sql = 'SELECT 
                * 
            FROM 
                `vvt_spread_doubleegg_exchange_award` AS p
            WHERE
                （p.`act_type` = 4 or p.`act_type` = 5）
            AND
                p.`user_id` = ' .$user_id
            ;

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