mysql 多表删除陷阱（跨库schema+别名的语法错误问题）
* 登陆用户为demo
* 连接字符串串中指定默认库是demo
* 另一个数据库(schema)是demo2，demo用户拥有demo2的所有访问权限
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delete f,s from tableF f left join?tableS?s on f.fid=s.fid
- result=ok
?
delete f,s from?demo.tableF?f left join?demo.tableS?s on f.fid=s.fid
- result=ok
?
delete f,s from?demo2.tableF?f left join?demo2.tableS s on f.fid=s.fid
- result=error,bad sql grammar :(
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delete?demo2.tableF,demo2.tableS?from?demo2.tableF?left join?demo2.tableS on?demo2.tableF.fid=demo2.tableS.fid
- result=ok
