PHP/Mysql 搜索 - 区分大小写

Question

Im using the following PHP and MySql to fetch rows from a table,

$search_word=$_GET['search_word'];
$search_word_new=mysql_escape_string($search_word);
$search_word_fix=str_replace(" ","%",$search_word_new);
$sql=mysql_query("SELECT * FROM tweets WHERE content LIKE '%$search_word_fix%' ORDER BY votes DESC LIMIT 20");

The 'content' field is a TEXT field containing tweets.

The problem I have is if I search ' S tackoverflow' I get all the results containing 'Stackoverflow' but no results when the text is ' s tackoverflow'. Basically the search is case sensitive.

Is it possible to change the query or PHP so when searching for 'Stackoverflow' both upper and lower case results are returned?

Answer 1

You can try:

$search_word_fix=strtolower(str_replace(" ","%",$search_word_new));
$sql=mysql_query("SELECT * FROM tweets WHERE lower(content) LIKE '%$search_word_fix%' ORDER BY votes DESC LIMIT 20");

• I've added strtolower to make $search_word_fix all lower case.
• And in the where clause I've changed content to lower(content) so that I compare with lowercase of content .

You could have made both these changes in the query as suggested in other answer.

Answer 2

Force the cases of both the search term and the column value:

SELECT * FROM tweets WHERE LOWER(content) LIKE LOWER('%$search_word_fix%') ORDER BY votes DESC LIMIT 20

or:

SELECT * FROM tweets WHERE UPPER(content) LIKE UPPER('%$search_word_fix%') ORDER BY votes DESC LIMIT 20

http://dev.mysql.com/doc/refman/5.0/en/string-functions.html

Answer 3

The 'proper' way to do it is to set it to case-insensitive collation:

CREATE TABLE foo (col1 varchar(24) COLLATE utf8_bin,col2 varchar(24) COLLATE  utf8_general_ci);
Query OK, 0 rows affected (0.03 sec)

DB 5.1.49-1-log:test  mysql> INSERT INTO foo VALUES ('stackoverflow','stackoverflow');
Query OK, 1 row affected (0.01 sec)

DB 5.1.49-1-log:test  mysql> SELECT * FROM foo WHERE col1 LIKE 'Stackoverflow';
Empty set (0.00 sec)

DB 5.1.49-1-log:test  mysql> SELECT * FROM foo WHERE col2 LIKE 'Stackoverflow';
+---------------+---------------+
| col1          | col2          |
+---------------+---------------+
| stackoverflow | stackoverflow |
+---------------+---------------+
1 row in set (0.00 sec)

DB 5.1.49-1-log:test  mysql> SELECT * FROM foo WHERE col1 COLLATE utf8_general_ci LIKE 'Stackoverflow';
+---------------+---------------+
| col1          | col2          |
+---------------+---------------+
| stackoverflow | stackoverflow |
+---------------+---------------+
1 row in set (0.00 sec)

Answer 4

Change the COLLATION of the column in question ( content ) to be case insensitive, such as utf8mb4_unicode_ci .

Doing the case folding in PHP is costly and inefficient.

Answer 5

mysql> SELECT * FROM myDb.myTable WHERE username = 'test980'; 1 row in set (0.00 sec)

mysql> SELECT * FROM myDb.myTable WHERE username = 'TEST980'; Empty set (0.00 sec)

MySQL columns can be made case-sensitive by creating them with the binary keyword. I suspect this is your problem. You can modify the column not to be binary or change your query to:

SELECT * FROM myDb.myTable WHERE UCASE(username) = 'TEST980';

which effectively makes string comparisons case insensitive despite the Binary character set chosen.

Answer 6

It's all about choosing the best collation when creating MySql database.

• utf8_unicode_ci is useful if you want to sort for example german character set accurately but it's slow.
• utf8_general_ci is by default the standard when creating MySQL database character set utf8 and it's the fastest, but not case sensitive.
• Rule of thumb: Use always utf8_general_ci on MySQL and collate utf8_bin if case sensitive required OR use SELECT BINARY in your statement.

Answer 7

请注意，如果您使用另一种语言并且您正在使用“strtolower()”，它不会将特殊字符（非英文字母）转换为小写，这将完成工作 mb_strtolower($text, 'utf8');