解决方案
20
至少5.1已经有DUAL
You are allowed to specify DUAL as a dummy table name in situations where no tables are referenced:
mysql> SELECT 1 + 1 FROM DUAL;
-> 2
DUAL is purely for the convenience of people who require that all SELECT statements should have FROM and possibly other clauses. MySQL may ignore the clauses. MySQL does not require FROM DUAL if no tables are referenced
You are allowed to specify DUAL as a dummy table name in situations where no tables are referenced:
mysql> SELECT 1 + 1 FROM DUAL;
-> 2
DUAL is purely for the convenience of people who require that all SELECT statements should have FROM and possibly other clauses. MySQL may ignore the clauses. MySQL does not require FROM DUAL if no tables are referenced
15
3.mysql的dual一般在什么清下使用？
DUAL is purely for the convenience of people who require that all SELECT statements should have FROM and possibly other clauses
DUAL is purely for the convenience of people who require that all SELECT statements should have FROM and possibly other clauses
5
与ORACLE中的没什么差别。
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