mysql - sql union 不规则组合

Question

查询3张表，最后一张表多了一行要查找。
试过这个:

(SELECT 't1' AS tn, navid, clicks AS cc, tags 
FROM t1 
WHERE DATE_ADD(d, INTERVAL '0 8' DAY_HOUR) <= NOW() 
AND tags LIKE '%cars%' )

UNION DISTINCT

(SELECT 't2' AS tn, navid, clicks AS cc, tags 
FROM t2 
WHERE DATE_ADD(d, INTERVAL '0 8' DAY_HOUR) <= NOW() 
AND tags LIKE '%cars%' )

UNION DISTINCT

(SELECT 't3' AS tn, navid, title, clicks AS cc, tags 
FROM t3 
WHERE DATE_ADD(d, INTERVAL '0 8' DAY_HOUR) <= NOW() 
AND tags LIKE '%cars%' ) 

我想获取 t3 中的 title 字段
任何帮助，谢谢

Answer 1

只需在前两个子查询中添加它，其值为NULL:

(SELECT 't1' AS tn, navid, NULL as title, clicks AS cc, tags 
 FROM t1 
 WHERE DATE_ADD(d, INTERVAL '0 8' DAY_HOUR) <= NOW() 
       AND tags LIKE '%cars%' )
UNION DISTINCT
(SELECT 't2' AS tn, navid, NULL as title, clicks AS cc, tags 
 FROM t2 
 WHERE DATE_ADD(d, INTERVAL '0 8' DAY_HOUR) <= NOW() 
       AND tags LIKE '%cars%' )
UNION DISTINCT
(SELECT 't3' AS tn, navid, title, clicks AS cc, tags 
 FROM t3 
 WHERE DATE_ADD(d, INTERVAL '0 8' DAY_HOUR) <= NOW() 
       AND tags LIKE '%cars%' )