MySQL Like 语句默认不区分大小写

Question

As far as I know, LIKE statements in MySQL are case-insensitive by default as shown here .

In my case, it seems they are not, for instance SELECT * FROM users WHERE CONCAT(name, ' ', surname) LIKE '%rob%' doesn't return anything, while SELECT * FROM users WHERE CONCAT(name, ' ', surname) LIKE '%Rob%' returns a record whose "name" column is "Robert".

I want SELECT * FROM users WHERE CONCAT(name, ' ', surname) LIKE '%rob%' to return the record whose "name" column is "Robert".

Answer 1

SELECT * FROM users WHERE LOWER(CONCAT(name, ' ', surname)) LIKE '%rob%'

Answer 2

As far as I know, LIKE statements in MySQL are case-insensitive by default as shown here.

The information described in this article is not correct. The case sensitivity in string operations depends on the collation.

MySQL 8.0 Reference Manual / Character Sets, Collations, Unicode .

 CREATE TABLE test (txt_ai_ci VARCHAR(255) COLLATE utf8mb4_0900_ai_ci, txt_as_cs VARCHAR(255) COLLATE utf8mb4_0900_as_cs); INSERT INTO test VALUES ('GREEN', 'GREEN'), ('Green', 'Green'), ('green', 'green');

 SELECT txt_ai_ci, txt_ai_ci LIKE 'Gr%', txt_as_cs, txt_as_cs LIKE 'Gr%', txt_as_cs COLLATE utf8mb4_0900_ai_ci LIKE 'Gr%' FROM test 

txt_ai_ci	txt_ai_ci LIKE 'Gr%'	txt_as_cs	txt_as_cs LIKE 'Gr%'	txt_as_cs COLLATE utf8mb4_0900_ai_ci LIKE 'Gr%'
GREEN	1	GREEN	0	1
Green	1	Green	1	1
green	1	green	0	1

db<>fiddle here