对于查询情况,其实MySQL提供给我们一个功能来引导优化器更好的优化,那便是MySQL的查询优化提示(Query Optimizer Hints)。比如,想让SQL强制走索引的话,可以使用 FORCE INDEX 或者USE INDEX;它们基本相同,不同点:在于就算索引的实际用处不大,FORCE INDEX也得要使用索引。 EXPLAIN SELECT * FROM yp_user FORCE INDEX(...
http://dev.mysql.com/doc/refman/8.0/en/with.html.Single-TableSyntaxDELETE[LOW_PRIORITY][QUICK][IGNORE]FROMtbl_name[PARTITION (partition_name [, partition_name]...)][WHERE where_condition][ORDER BY ...][LIMIT row_count]TheDELETEstatement deletes rowsfromtbl_nameandreturnsthenumberofdeleted r...
DELETEFROMemployees;Code language:SQL (Structured Query Language)(sql) 3) Deleting related rows from multiple tables It becomes more complicated when you want to delete a row in a table that is associated with other rows in another table. ...
For more information, seeFROM (Transact-SQL). WHERE Specifies the conditions used to limit the number of rows that are deleted. If a WHERE clause is not supplied, DELETE removes all the rows from the table. There are two forms of delete operations based on what is specified in the WHERE...
A SQLDELETEstatement can includeJOINoperations. It can contain zero, one, or multiple JOIN operations. The DELETE removes records that satisfy the JOIN conditions. Example # Remove products that have not sold. DELETEPFROMProduct PLEFTJOINOrderItem IONP.Id=I.ProductIdWHEREI.IdISNULL ...
For more information, see FROM (Transact-SQL).WHERE Specifies the conditions used to limit the number of rows that are deleted. If a WHERE clause is not supplied, DELETE removes all the rows from the table.There are two forms of delete operations based on what is specified in the WHERE ...
开始我们拿sql到数据库查询平台查库执行计划,无奈这个平台有bug,delete语句无法查看,所以我们改成select,“应该”是一样。这个“应该”加了双引号,导致我们走了一点弯路。 EXPLAINSELECT*fromt_table_1wheretask_idin(selectidfromt_table_2whereuid=1)
开始我们拿sql到数据库查询平台查库执行计划,无奈这个平台有bug,delete语句无法查看,所以我们改成select,“应该”是一样。这个“应该”加了双引号,导致我们走了一点弯路。 EXPLAIN SELECT * from t_table_1 where task_id in (select id from t_table_2 where uid = 1) ...
DELETE,MaxCompute:Deletes one or more rows of data that meets the specified conditions from a partitioned transactional table or a non-partitioned transactional table.
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