Question

我有一个包含2列别名（全部为小写）和排序

的表格

如何根据字母别名按字母顺序将数字0设置为x？

根据另一个查询的排序顺序更新列（按别名选择mytable顺序）？

to get

alias         |   ordering
abf-ergterw   |   0
crdsv-dfgdfg  |   2
bggg-rgewrdg  |   1
dxgg-rgewrdg  |   3

类似

SET @count = 0;
UPDATE mytable SET ordering = @count:= @count + 1;

但基于列别名 a = 1，b = 2，c = 3，....

谢谢

Answer 1

您可以使用ROW_NUMBER：

SELECT *, ROW_NUMBER() OVER(ORDER  BY alias ASC) - 1 AS ordering
FROM tab
ORDER BY ordering;

UPDATE：

UPDATE tab a
JOIN (
  SELECT *, ROW_NUMBER() OVER(ORDER  BY alias ASC) - 1 AS ord
  FROM tab
  ) b ON a.alias = b.alias
SET a.ordering = b.ord
;

Answer 2

您可以在UPDATE语句中使用ORDER BY子句：

SET @count = -1;
UPDATE mytable
SET ordering = @count:= @count + 1
ORDER BY alias ASC;