Updating in sql
This option takes a list of one or more partitions or subpartitions (or both).Only the partitions (or subpartitions) listed are checked for matches, and a row that is not in any of these partitions or subpartitions is not updated, whether it satisfies the clause, are flagged as unsafe for statement-based replication.
If you update a column that has been declared , an error occurs if strict SQL mode is enabled; otherwise, the column is set to the implicit default value for the column data type and the warning count is incremented. This facilitates to update table1 column with expression whose corresponding value from table2 is returned as NULL It took me a few minutes to figure this out, but the syntax for UPDATING ONE TABLE ONLY using a relationship between two tables in My SQL 4.0 is actually quite simple:update t1, t2 set t1.field = t2.value where t1= t2.that; It should be noted that even simple applications of UPDATE can conflict with the 'safe mode' setting of the mysql daemon.The solution is surprisingly simple, thanks to My SQL: UPDATE xoops_bb_posts_text SET post_text=( REPLACE (post_text, 'morphix.sourceforge.net', ' the string function REPLACE, all items in the post_text column with 'morphix.sourceforge.net' get this substring replaced by 'Ideal when writing a script is just too much effort.So, here it is again.]A very server resources friendly method to update multiple rows in the same table is by using WHEN THEN (with a very important note).UPDATE tbl_name SET fld2 = CASE fld1WHEN val1 THEN data1WHEN val2 THEN data2ELSE fld2 ENDThe note is: do not forget ELSE.