SQL 错误 [1064] [42000]：在 Z81C3B080DAD537DE7EZE10E0987A4BF58 上使用 ALTER IGNORE TABLE 时，您的 SQL 语法有错误

Question

This one works in older mysql versions, but the good thing with this query is that it will remove duplicates and same time add index, how do i do the same in mysql 8 commercial

ALTER IGNORE TABLE tablex
ADD UNIQUE INDEX id_rmd (field1,field12, field3);

SQL Error [1064] [42000]: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IGNORE TABLE...

How do i do the same in mysql 8 commercial. ie remove duplicate while same time create index

Answer 1

Commercial or not doesn't make a difference. This 5.6 and earlier feature is removed in later versions.

https://dev.mysql.com/doc/refman/5.6/en/alter-table.html :

IGNORE is a MySQL extension to standard SQL. It controls how ALTER TABLE works if there are duplicates on unique keys in the new table or if warnings occur when strict mode is enabled. If IGNORE is not specified, the copy is aborted and rolled back if duplicate-key errors occur. If IGNORE is specified, only one row is used of rows with duplicates on a unique key. The other conflicting rows are deleted. Incorrect values are truncated to the closest matching acceptable value.

You can just rename and copy the table (untested):

create tablex_new like tablex;
ALTER TABLE tablex_new
ADD UNIQUE INDEX id_rmd (field1,field12, field3);
insert ignore into tablex_new select * from tablex;
rename tablex to tablex_old, tablex_new to tablex;
drop table tablex_old;