Question

我有一个声明我的工作方式，但是它是正确的方式，因为我有很多IF语句，并想知道它是否对性能有影响，或者我应采取不同的方法进行最佳实践。这是从阅读文档创建的，所以我可能已经走了它的日志方式。

SELECT c.id, c.first_name, c.last_name, 
IF( c.id IN  (SELECT client_id  FROM bookings)  AND '1' IN (SELECT practitioner_id FROM bookings) , c.address1, NULL) as address1,
IF( c.id IN  (SELECT client_id  FROM bookings)  AND '1' IN (SELECT practitioner_id FROM bookings) , c.address2, NULL) as address2,  
IF( c.id IN  (SELECT client_id  FROM bookings)  AND '1' IN (SELECT practitioner_id FROM bookings) , c.town, NULL) as town, 
IF( c.id IN  (SELECT client_id  FROM bookings)  AND '1' IN (SELECT practitioner_id FROM bookings) , c.county, NULL) as county,  
IF( c.id IN  (SELECT client_id  FROM bookings)  AND '1' IN (SELECT practitioner_id FROM bookings) , c.postcode, NULL) as postcode,  
IF( c.id IN  (SELECT client_id  FROM bookings)  AND '1' IN (SELECT practitioner_id FROM bookings) , c.email, NULL) as email,  
IF( c.id IN  (SELECT client_id  FROM bookings)  AND '1' IN (SELECT practitioner_id FROM bookings) , c.dob, NULL) as dob 
FROM clients c

Answer 1

你应该采取不同的方法。

我猜你在相应的预订有1的从业者时想要额外的列。我不是100％肯定，因为你的查询做了一些稍微不同的事情。

但总体思路是这样的：

SELECT c.id, c.first_name, c.last_name,
       (CASE WHEN b.client_id IS NOT NULL THEN c.address1 END) as address1,
       . . .
FROM clients c LEFT JOIN
     bookings b
     ON c.id = b.client_id AND b.practitioner_id = 1;

使用您想要的其他列填写. . .。

如果值在另一个表中，则选择某些列

1 个答案: