mysql - 在 mysql 查询中使用 if 语句

Question

我想在 sql 查询中使用 if 语句:

我想要什么:

if(tractions_delivery.send_date_id !=0 ){

           date_send_commodities.id  = tractions_delivery.send_date_id
}

---

我的查询:

        from

            tractions_delivery,user_address,province,city,date_send_commodities,users

        WHERE

        tractions_delivery.tr_id = $tr_id
        AND
        tractions_delivery.address_id = user_address.id
        AND
        user_address.province_id = province.id
        AND
        user_address.city_id      = city.id
        AND
        //not work
        (tractions_delivery.send_date_id IS NOT 0 date_send_commodities.id  = tractions_delivery.send_date_id)

        AND
        users.id = user_address.user_id

Answer 1

你可以使用 CASE 语句

SELECT 
*
FROM
 tractions_delivery,
 user_address,
 province,
 city,
 date_send_commodities,users
WHERE
 tractions_delivery.tr_id = $tr_id AND
 tractions_delivery.address_id = user_address.id AND
 user_address.province_id = province.id AND
 user_address.city_id = city.id AND
 CASE WHEN tractions_delivery.send_date_id != 0 THEN date_send_commodities.id = tractions_delivery.send_date_id ELSE 1=1 END AND
 users.id = user_address.user_id