MYSQL一些不常用的函数笔记
字符串替换
REPLACE ( fieldname, search, replace )
数据去重
DELETE ...
DELETE FROM table_copy
WHERE key IN (
SELECT t.key FROM (
SELECT key FROM table_copy GROUP BY key having count(*) >1
) t
)
AND id NOT IN(
SELECT t.id FROM (
SELECT id FROM table_copy GROUP BY key having count(*) >1
) t
)
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