SQL common statement record

choose

Format:

<choose>

<when ​​test=condition 1>

the code executed;

</when>

<when ​​test=condition 2>

the code executed;

</when>

......

<otherwise>

    the code executed;

</when>

</otherwise>

</choose>

Note: until the condition is established, other judgments will not be implemented

————————————————

First, check whether there is a record in the database according to the value of a certain field, update it if it exists, and insert it if it does not.

ON DUPLICATE key update

————————————————————————————————