标签 mysql 下的文章

MySql经常用,但是通常就是ORM中间件来CRUD操作,很少关注索引问题,可能是我近些年很少用MySQL做大型的系统了。
现在一面试就遇到所有领域的问题来都来一个问一遍,MySQL的复合索引其实也就一知半解。

面试官的问类似于select语句里where a>100 and b=3 and c=1 能否命中创建的(a, b, c)这种索引,还有a>100能否命中这个复合索引。

我想当然就说,a>100 and b=3 and c=1 只能命令(a, b, c)这种索引, a>100不能命中。唉呀,人家笑了。我说我可能说的不对,我下来试试。好吧查资料,建表,亲自实操一把。


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Check what's the CONSTRAINT name and the FOREIGN KEY name:

SHOW CREATE TABLE table_name;

Remove both the CONSTRAINT name and the FOREIGN KEY name:

ALTER TABLE table_name
  DROP FOREIGN KEY the_name_after_CONSTRAINT,
  DROP KEY the_name_after_FOREIGN_KEY;

Or simply run this if you know the foreign key name:

alter table footable drop foreign key fooconstraint

原文:https://stackoverflow.com/questions/838354/mysql-removing-some-foreign-keys

Background

mysql server was installed by brew install mysql

Issues like this:

ERROR: Failed building wheel for mysqlclient

ld: library not found for -lssl
clang: error: linker command failed with exit code 1 (use -v to see invocation)
error: command 'clang' failed with exit status 1

Exception: Wrong MySQL configuration: maybe https://bugs.mysql.com/bug.php?id=86971 ?



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