Question

鉴于table1，table2和table3（假设它们在结构上相同），是否可以选择table1，table2和table3的前1/3记录？然后第二个1/3？然后是最后的1/3？

Answer 1

前1/3记录：

SELECT *
FROM
(
    SELECT *
    FROM
    (
       SELECT * FROM Table1 
       UNION ALL 
       SELECT * FROM Table2
       UNION ALL
       SELECT * FROM Table3 
       UNION ALL
    ) sub
    ORDER BY ID DESC
    LIMIT 3
) t 
ORDER BY Id ASC
LIMIT 1

第二个2/3 ::

SELECT *
FROM
(
    SELECT *
    FROM
    (
       SELECT * FROM Table1 
       UNION ALL 
       SELECT * FROM Table2
       UNION ALL
       SELECT * FROM Table3 
       UNION ALL
    ) sub
    ORDER BY ID DESC
    LIMIT 3
) t 
ORDER BY Id ASC
LIMIT 2, 1

最后1/3记录：

SELECT *
FROM
(
    SELECT *
    FROM
    (
       SELECT * FROM Table1 
       UNION ALL 
       SELECT * FROM Table2
       UNION ALL
       SELECT * FROM Table3 
       UNION ALL
    ) sub
    ORDER BY ID DESC
    LIMIT 3
) t 
ORDER BY Id DESC
LIMIT 1

Answer 2

尝试使用LIMIT和OFFSET子句，如：

SELECT column FROM table1 LIMIT X OFFSET Y
union
SELECT column FROM table2 LIMIT X OFFSET Y+10
union
SELECT column FROM table3 LIMIT X OFFSET Y+20

但你必须参数化LIMIT和OFFSET ..这是一种方式

MySQL - 从多个表中选择第一个，第二个第三个和第三个第三个

2 个答案: