I need to make this update query more efficient.
UPDATE #table_name# SET #column_name2# = 1 WHERE #column_name1# in (A list of data)
Right now it takes more than 2 minute to finish the job when my list of data is quite large. Here is the result of explain of this query:
+----+-------------+--------------+-------+---------------+---------+---------+------+--------+------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------------+-------+---------------+---------+---------+------+--------+------------------------------+
| 1 | SIMPLE | #table_name# | index | NULL | PRIMARY | 38 | NULL | 763719 | Using where; Using temporary |
+----+-------------+--------------+-------+---------------+---------+---------+------+--------+------------------------------+
In class, I was told that an OK query should at least have a type of range
and is better to reach ref
. Right now mine is index
, which is the second slowest I think. I'm wondering if there's a way to optimize that.
Here is the table format:
+--------------------+-------------+------+-----+-------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------------+-------------+------+-----+-------------------+-------+
| #column_name1# | varchar(12) | NO | PRI | | |
| #column_name2# | tinyint(4) | NO | | 0 | |
| #column_name3# | tinyint(4) | NO | | 0 | |
| ENTRY_TIME | datetime | NO | | CURRENT_TIMESTAMP | |
+--------------------+-------------+------+-----+-------------------+-------+
My friend suggested me that using exists
rather than in
clause may help. However, it looks like I cannot use exists
like exists (A list of data)
For this query:
UPDATE #table_name#
SET #column_name2# = 1
WHERE #column_name1# in (A list of data);
You want an index on #table_name#(#column_name1#)
.
Do note that the number of records being updated has a very big impact on performance. If the "list of data" is really a subquery, then other methods are likely to be more helpful for improving performance.
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