U ka sebelisa MySQL joang moo polelo? moo poleloana e 'maloa ea syntax e nang le maemo

Mokhoa oa ho sebelisa poleloana ea WHERE ho MySQL ? Syntax bakeng sa maemo a mangata poleloaneng ea WHERE.

MySQL MANE clause

Re tseba ho sebelisa polelo ea SQL SELECT ho bala lintlha tse tsoang tafoleng ea MySQL.

Ho khetha data ho tsoa tafoleng, eketsa poleloana ea WHERE ho polelo ea KHETHA.

sebōpeho-puo

Se latelang ke syntax e akaretsang ea polelo ea SQL SELECT ho bala data ho tsoa tafoleng ea data ho sebelisa poleloana ea WHERE:

SELECT field1, field2,...fieldN FROM table_name1, table_name2...
[WHERE condition1 [AND [OR]] condition2.....

• U ka sebelisa tafole e le 'ngoe kapa ho feta polelong ea potso, u sebelisa liphehelo lipakeng tsa litafole, Arola, 'me u sebelise polelo ea WHERE ho beha maemo a potso.
• O ka hlakisa boemo bofe kapa bofe ho poleloana ea WHERE.
• O ka hlakisa maemo a le mong kapa a mangata o sebelisa AND kapa OR.
• Temana ea WHERE e ka boela ea sebelisoa ka litaelo tsa SQL's DELETE kapa UPDATE.
• Temana ea WHERE e tšoana le haeba boemo ba puo ea lenaneo, ho bala lintlha tse boletsoeng ho latela boleng ba tšimo tafoleng ea MySQL.

Lenane le latelang ke la li-operators tse ka sebelisoang ho poleloana ea WHERE.

Mehlala e tafoleng e ka tlase e nka hore A ke 10 le B ke 20

Temana ea WHERE e thusa haholo haeba re batla ho bala data e boletsoeng ho tsoa tafoleng ea data ea MySQL.

Ho sebelisa senotlolo sa mantlha joalo ka potso e nang le maemo ho poleloana ea WHERE ho potlakile haholo.

Haeba litekanyetso tse fanoeng li se na lirekoto tse tšoanang tafoleng, potso ha e khutlisetse data.

bala data ho tsoa ho taelo ea litaelo

Re tla sebelisa poleloana ea WHERE polelong ea SQL SELECT ho bala lintlha tse tafoleng ea data ea MySQL chenweiliang_tbl:

Mohlala

Mohlala o latelang o tla bala lirekoto tsohle tafoleng ea chenweiliang_tbl moo boleng ba sebaka sa chenweiliang_author e leng Sanjay:

Papiso ea likhoele ho MySQL's WHERE clause ha e na taba.U ka sebelisa lebitso la bohlokoa la BINARY ho hlakisa hore papiso ea likhoele ho WHERE clause e na le taba-tabelo.

Mohlala o latelang:

mysql> SELECT * from chenweiliang_tbl WHERE BINARY chenweiliang_author='chenweiliang.com';
Empty set (0.01 sec)
 
mysql> SELECT * from chenweiliang_tbl WHERE BINARY chenweiliang_author='chenweiliang.com';
+-----------+---------------+---------------+-----------------+
| chenweiliang_id | chenweiliang_title | chenweiliang_author | submission_date |
+-----------+---------------+---------------+-----------------+
| 3 | JAVA 教程 | chenweiliang.com | 2016-05-06 |
| 4 | 学习 Python | chenweiliang.com | 2016-03-06 |
+-----------+---------------+---------------+-----------------+
2 rows in set (0.01 sec)

Mohlala o sebedisa lentswe la bohlokwa la BINARY , le nang le mongolo o bobebe, kahoo boemo ba potso chenweiliang_author='chenweiliang.com' ha bo kgutlise data.

Bala lintlha u sebelisa mongolo oa PHP

U ka sebelisa mosebetsi oa PHP mysqli_query() le taelo e tšoanang ea SQL SELECT ka poleloana ea WHERE ho fumana lintlha.

Mosebetsi ona o sebelisetsoa ho phethahatsa litaelo tsa SQL ebe o hlahisa lintlha tsohle tse botsitsoeng ka PHP function mysqli_fetch_array().

Mohlala

Mohlala o latelang o tla khutlisa direkoto tse tswang tafoleng ya chenweiliang_tbl tse sebedisang boleng ba chenweiliang_author tshimong ya chenweiliang_author jwalo ka chenweiliang.com :

Teko ea polelo ea MySQL WHERE:

<?
php
$dbhost = 'localhost:3306'; // mysql服务器主机地址
$dbuser = 'root'; // mysql用户名
$dbpass = '123456'; // mysql用户名密码
$conn = mysqli_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
 die('连接失败: ' . mysqli_error($conn));
}
// 设置编码，防止中文乱码
mysqli_query($conn , "set names utf8");
 
// 读取 chenweiliang_author 为 chenweiliang.com 的数据
$sql = 'SELECT chenweiliang_id, chenweiliang_title, 
 chenweiliang_author, submission_date
 FROM chenweiliang_tbl
 WHERE chenweiliang_author="chenweiliang.com"';
 
mysqli_select_db( $conn, 'chenweiliang' );
$retval = mysqli_query( $conn, $sql );
if(! $retval )
{
 die('无法读取数据: ' . mysqli_error($conn));
}
echo '<h2>陈沩亮博客 MySQL WHERE 子句测试<h2>';
echo '<table border="1"><tr><td>教程 ID</td><td>标题</td><td>作者</td><td>提交日期</td></tr>';
while($row = mysqli_fetch_array($retval, MYSQL_ASSOC))
{
 echo "<tr><td> {$row['chenweiliang_id']}</td> ".
 "<td>{$row['chenweiliang_title']} </td> ".
 "<td>{$row['chenweiliang_author']} </td> ".
 "<td>{$row['submission_date']} </td> ".
 "</tr>";
}
echo '</table>';
// 释放内存
mysqli_free_result($retval);
mysqli_close($conn);
?>