MySQL Hint: illegal mix of collations for operation ' UNION '

Source: Internet
Author: User


The statement is simple

The code is as follows Copy Code

<?php
$connection =mysql_connect ("localhost", "root", "password"); Connect and select a database server
mysql_select_db ("Test", $connection);
$query = "SELECT * from users where name= ' Hello '";
$result =mysql_query ($query, $connection);
while ($row =mysql_fetch_array ($result))
{
echo "User id:". $row [0]. " <br> "; can also write $row["user_id"]
echo "Username:". $row [1]. " <br> "; can also write $row["user_name"]
}
?>

Run Results prompt

Error:illegal mix of collations (gbk_chinese_ci,implicit) and (latin1_swedish_ci,coercible) for operation ' = '

It means: the operator "=" compares the character set inconsistency, one is gbk_chinese_ci, the other is latin1_swedish_ci.

First, view the MySQL my.cnf, confirmed as UTF8

The code is as follows Copy Code


Mysql> Show variables like "%char%";

+--------------------------+-------------------------------------+

| variable_name | Value |

+--------------------------+-------------------------------------+

| character_set_client | UTF8 |

| character_set_connection | UTF8 |

| Character_set_database | Latin1 |

| Character_set_filesystem | binary |

| Character_set_results | UTF8 |

| Character_set_server | UTF8 |

| Character_set_system | UTF8 |

| Character_sets_dir | D:/mysql Server 5.0/share/charsets/|

+--------------------------+-------------------------------------+

8 rows in Set (0.00 sec)


Mysql> Show variables like "%coll%";

+----------------------+-------------------+

| variable_name | Value |

+----------------------+-------------------+

| collation_connection | Utf8_general_ci |

| Collation_database | Latin1_swedish_ci |

| Collation_server | Utf8_general_ci |

+----------------------+-------------------+

3 Rows in Set (0.00 sec)

Then change all encodings in the database to uniform:

The code is as follows Copy Code


Mysql> set Character_set_database=utf8;

Query OK, 0 rows Affected (0.00 sec)

Mysql> Set collation_database= utf8_general_ci

Re-view character set and data table field encoding characters are consistent:


Summary

Utf8_bin
Utf8_general_ci
Utf8_unicode_ci

Utf8_bin and Utf8_general_ci can

Utf8_bin and Utf8_unicode_ci can

Utf8_general_ci and Utf8_unicode_ci not allowed

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