MySQL 每列的最小值和最大值

Question

我可以运行以下命令来动态识别具有多列的表中的所有小数字段:

SELECT COLUMN_NAME, DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME='tbl_name' AND DATA_TYPE = 'decimal'

我如何提取每个字段的最小值和最大值？例如最终输出如下:

COLUMN_NAME  DATA_TYPE  MIN_VAL  MAX_VAL
a            decimal    4        22
b            decimal    18       5593
c            decimal    1        299

<小时/>

更新:

这是我用来实现此功能的最终语法。也许我错过了一个更简单的方法，但这是有效的，所以感谢戈登·利诺夫的回答。

set @sql = concat('SELECT ', @cols, ' FROM ', @t);

SELECT @sql := GROUP_CONCAT(REPLACE(REPLACE(@sql, @cols,
                                            CONCAT('"', COLUMN_NAME, '" as TheCol', ', ', '"', DATA_TYPE, '" as TheDType', ', ',
                                                   'MIN(', COLUMN_NAME, ') as TheMin, MAX(', COLUMN_NAME, ') as TheMax'
                                                  )
                                           ),
                                    @t, 'tbl_name') SEPARATOR ' union all '
                            )              
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME='tbl_name' AND DATA_TYPE = 'decimal';

prepare s from @sql;
execute s;
deallocate prepare s;

Answer 1

您需要使用动态sql:

set @sql = 'SELECT @cols FROM @t';

SELECT @sql := GROUP_CONCAT(REPLACE(REPLACE(@sql, @cols,
                                            CONCAT(COLUMN_NAME, ', ', DATA_TYPE, ', ',
                                                   'MIN(', COLUMN_NAME, '), MAX(', COLUMN_NAME, ')'
                                                  )
                                           ),
                                    @t, 'tbl_name') SEPARATOR ' union all '
                            )              
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME='tbl_name' AND DATA_TYPE = 'decimal';

prepare s from @sql;
execute s;
deallocate prepare s;