mysql - SQL 查询语法

Question

编辑:

我有一张表:比如说 TABLE1，这是数据:

--------------------------
COL1 | COL2 | COL3 | COL4
--------------------------
 1   |  10  | 100  | 1000
 1   |  10  | 100  | 1000
 1   |  10  | 100  | 1000
--------------------------

然后说 TABLE2，

---------------------------
ID | COL_NAMES
---------------------------
1  | COL3
2  | COL4
---------------------------

现在我要做的是从表 2 中选择列名，对于这个列名，将表 1 中的所有值设置为 0， 这应该是最终结果:

--------------------------
COL1 | COL2 | COL3 | COL4
--------------------------
 1   |  10  |   0  |    0
 1   |  10  |   0  |    0
 1   |  10  |   0  |    0
--------------------------

如何编写查询？

Answer 1

如果你想在 Table1 上SELECT，你可以这样做:

SELECT CONCAT('SELECT ', GROUP_CONCAT(c.COLUMN_NAME),',',
(SELECT GROUP_CONCAT(0,' as ',t2.COL_NAMES) FROM table2 t2),' FROM table1;')
INTO @query
FROM INFORMATION_SCHEMA.COLUMNS c
WHERE c.TABLE_NAME = 'table1'
AND c.COLUMN_NAME not in (select COL_NAMES from table2)
ORDER BY c.ORDINAL_POSITION;

PREPARE stmt FROM @query;
EXECUTE stmt;

SELECT Query

如果你想更新 table1，你可以使用这个查询来更新它:

SELECT CONCAT('UPDATE TABLE1 SET ', GROUP_CONCAT(c.COLUMN_NAME, ' = ', 0) )
INTO @query
FROM INFORMATION_SCHEMA.COLUMNS c
WHERE c.TABLE_NAME = 'table1'
AND c.COLUMN_NAME in (select COL_NAMES from table2)
ORDER BY c.ORDINAL_POSITION;

PREPARE stmt FROM @query;
EXECUTE stmt;

UPDATE Query