How can I make SQL case sensitive string comparison on MySQL?

mysql sql interop case-sensitive string-comparison

299,498

Solution 1

http://dev.mysql.com/doc/refman/5.0/en/case-sensitivity.html

The default character set and collation are latin1 and latin1_swedish_ci, so nonbinary string comparisons are case insensitive by default. This means that if you search with col_name LIKE 'a%', you get all column values that start with A or a. To make this search case sensitive, make sure that one of the operands has a case sensitive or binary collation. For example, if you are comparing a column and a string that both have the latin1 character set, you can use the COLLATE operator to cause either operand to have the latin1_general_cs or latin1_bin collation:

col_name COLLATE latin1_general_cs LIKE 'a%'
col_name LIKE 'a%' COLLATE latin1_general_cs
col_name COLLATE latin1_bin LIKE 'a%'
col_name LIKE 'a%' COLLATE latin1_bin

If you want a column always to be treated in case-sensitive fashion, declare it with a case sensitive or binary collation.

Solution 2

The good news is that if you need to make a case-sensitive query, it is very easy to do:

SELECT *  FROM `table` WHERE BINARY `column` = 'value'

Solution 3

The answer posted by Craig White has a big performance penalty

SELECT *  FROM `table` WHERE BINARY `column` = 'value'

because it doesn't use indexes. So, either you need to change the table collation like mention here https://dev.mysql.com/doc/refman/5.7/en/case-sensitivity.html.

Easiest fix, you should use a BINARY of value.

SELECT *  FROM `table` WHERE `column` = BINARY 'value'

E.g.

mysql> EXPLAIN SELECT * FROM temp1 WHERE BINARY col1 = "ABC" AND col2 = "DEF" ;
+----+-------------+--------+------+---------------+------+---------+------+--------+-------------+
| id | select_type | table  | type | possible_keys | key  | key_len | ref  | rows   | Extra       |
+----+-------------+--------+------+---------------+------+---------+------+--------+-------------+
|  1 | SIMPLE      | temp1  | ALL  | NULL          | NULL | NULL    | NULL | 190543 | Using where |
+----+-------------+--------+------+---------------+------+---------+------+--------+-------------+

mysql> EXPLAIN SELECT * FROM temp1 WHERE col1 = BINARY "ABC" AND col2 = "DEF" ;
+----+-------------+-------+-------+---------------+---------------+---------+------+------+------------------------------------+
| id | select_type | table | type  | possible_keys | key           | key_len | ref  | rows | Extra                              |
+----+-------------+-------+-------+---------------+---------------+---------+------+------+------------------------------------+
|  1 | SIMPLE      | temp1 | range | col1_2e9e898e | col1_2e9e898e | 93      | NULL |    2 | Using index condition; Using where |
+----+-------------+-------+-------+---------------+---------------+---------+------+------+------------------------------------+
enter code here

1 row in set (0.00 sec)

Solution 4

Instead of using the = operator, you may want to use LIKE or LIKE BINARY

// this returns 1 (true)
select 'A' like 'a'

// this returns 0 (false)
select 'A' like binary 'a'


select * from user where username like binary 'a'

It will take 'a' and not 'A' in its condition

Solution 5

The most correct way to perform a case sensitive string comparison without changing the collation of the column being queried is to explicitly specify a character set and collation for the value that the column is being compared to.

select * from `table` where `column` = convert('value' using utf8mb4) collate utf8mb4_bin;