Comments on: Running a case sensitive query in on a case insensitive table

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By: swanhart

swanhart — Thu, 27 Aug 2009 22:26:03 +0000

and creating a temporary table and scanning it isn’t expensive..

If you want a hybrid that can use an index:

select * from t1 where a = ‘darren’ and binary a = ‘Darren’

By: Matthew

Matthew — Thu, 27 Aug 2009 20:06:17 +0000

Converting the left side is expensive.

Add a bunch more random rows…

mysql> select count(*) from t1;
+———-+
| count(*) |
+———-+
| 393219 |
+———-+

add an index on `a`

mysql> alter table t1 add index (a);

mysql> select * from t1 where a = binary ‘darren’;
+——–+
| a |
+——–+
| darren |
+——–+
1 row in set (0.00 sec)

mysql> select * from t1 where binary a = ‘darren’;
+——–+
| a |
+——–+
| darren |
+——–+
1 row in set (0.21 sec)

If you enable profiling and check this second query you will see it is spending the majority of the time in “Sending data” state while it reads the whole index and converts it to binary.

mysql> explain select * from t1 where a = binary ‘darren’;
+—-+————-+——-+——-+—————+——+———+——+——+————————–+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+—-+————-+——-+——-+—————+——+———+——+——+————————–+
| 1 | SIMPLE | t1 | range | a | a | 23 | NULL | 3 | Using where; Using index |
+—-+————-+——-+——-+—————+——+———+——+——+————————–+
1 row in set (0.00 sec)

By: swanhart

swanhart — Thu, 27 Aug 2009 18:36:03 +0000

or you can convert the left side instead:
mysql> select * from t1 where binary a = ‘Darren’
-> ;
+——–+
| a |
+——–+
| Darren |
+——–+
1 row in set (0.00 sec)

By: swanhart

swanhart — Thu, 27 Aug 2009 18:32:37 +0000

Try this simpler way:

mysql> select * from t1 where a = ‘Darren’ collate latin1_bin;
+——–+
| a |
+——–+
| Darren |
+——–+
1 row in set (0.12 sec)