MySQL update updates How the tape query is implemented

Now to do a data migration, you need to update the relevant data, you need to update in MySQL, you cannot use the updated table as the query table.

To summarize:

One: When a single table is updated

For example: Update customer Set category = 1 WHERE deleteflag = 0 and name = ' 22 ';

Be careful not to subquery, MySQL is not allowed.

II: Complex update of the tape query

Such as:

Update TB A,
(Select Time,name
From TT) b
Set Time4=b.col
where A.name=b.name and a.time1=b.time;

Note the point:

1, update, the updated table cannot be used in the set and where in the subquery;

2, update, multiple tables can be updated (SQL Server does not work);

such as: Update Ta a,tb b set a.bid=b.id, b.aid=a.id;

3, after the update can do arbitrary query, this role is equivalent to from;

Reference article: Thank the original, took a half-day to get out, see here, enlightened.

http://blog.csdn.net/xys_777/article/details/5793565

MySQL update updates How the tape query is implemented