Pehea e hoʻohana ai i ka ʻōlelo MySQL kahi? kahi e hoʻopaʻa ai i nā syntax kūlana lehulehu

MySQL waihonaPehea e hoʻohana ai i ka ʻōlelo hea? kahi e hoʻopaʻa ai i nā syntax kūlana lehulehu

MySQL WHERE pauku

ʻIke mākou e hoʻohana i ka ʻōlelo SQL SELECT e heluhelu i ka ʻikepili mai ka papa MySQL.

No ke koho pono ʻana i ka ʻikepili mai kahi pākaukau, e hoʻohui i kahi māhele WHERE i ka ʻōlelo SELECT.

ʻōlelo ʻōlelo

ʻO kēia ka syntax maʻamau o kahi ʻōlelo SQL SELECT e heluhelu i ka ʻikepili mai kahi papa ʻikepili me ka hoʻohana ʻana i ka māhele WHERE:

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

• Hiki iā ʻoe ke hoʻohana i hoʻokahi a ʻoi aku paha nā papa ma ka ʻōlelo nīnau, me ka hoʻohana ʻana i nā koma ma waena o nā papa, E hoʻokaʻawale, a hoʻohana i ka ʻōlelo WHERE e hoʻonohonoho i nā kūlana nīnau.
• Hiki iā ʻoe ke kuhikuhi i kekahi kūlana ma ka māhele WHERE.
• Hiki iā ʻoe ke kuhikuhi i hoʻokahi a ʻoi aku paha nā kūlana me ka hoʻohana ʻana i ka AND a i ʻole OR.
• Hiki ke hoʻohana ʻia ka paukū WHERE me nā kauoha DELETE a i ʻole UPDATE a SQL.
• Ua like ka paukū WHERE me ke kūlana inā ma nā ʻōlelo kaʻina hana, a heluhelu i ka ʻikepili i kuhikuhi ʻia e like me ka waiwai kahua ma ka papa MySQL.

Eia ka papa inoa o nā mea hoʻohana i hiki ke hoʻohana ʻia ma ka paukū WHERE.

Manaʻo nā laʻana ma ka papa ma lalo he 10 ʻo A a ʻo B he 20

He mea maikaʻi loa ka paukū WHERE inā makemake mākou e heluhelu i ka ʻikepili i kuhikuhi ʻia mai ka papa ʻikepili MySQL.

ʻO ka hoʻohana ʻana i ke kī kumu ma ke ʻano he nīnau kūlana ma ka māhele WHERE he wikiwiki loa.

Inā ʻaʻohe moʻolelo pili i ka papa kuhikuhi i hāʻawi ʻia, ʻaʻole e hoʻihoʻi ʻia ka ʻikepili.

heluhelu ʻikepili mai ke kauoha kauoha

E hoʻohana mākou i ka paukū WHERE ma ka ʻōlelo SQL SELECT e heluhelu i ka ʻikepili ma ka papa ʻikepili MySQL chenweiliang_tbl:

laʻana

E heluhelu ana keia la'ana i na moolelo a pau ma ka papa chenweiliang_tbl kahi o Sanjay ka waiwai o ke kahua chenweiliang_author:

ʻO ka hoʻohālikelike ʻana i nā string ma MySQL WHERE clause he case-insensitive.Hiki iā ʻoe ke hoʻohana i ka huaʻōlelo BINARY e wehewehe i ka hoʻohālikelike ʻana i ke kaula ma ka paukū WHERE he hihia.

ʻO kēia laʻana:

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)

hoʻohana ʻia ma ka laʻana BINARI hua'ōlelo, he case-sensitive, no laila chenweiliang_author='chenweiliang.com' ʻAʻohe ʻikepili ke kūlana nīnau.

E heluhelu i ka ʻikepili me ka hoʻohana ʻana i ka palapala PHP

Hiki iā ʻoe ke hoʻohana i ka hana PHP mysqli_query() a me ke kauoha SQL SELECT like me kahi māhele WHERE e kiʻi i ka ʻikepili.

Hoʻohana ʻia kēia hana e hoʻokō i nā kauoha SQL a laila hoʻopuka i nā ʻikepili i nīnau ʻia ma o ka hana PHP mysqli_fetch_array().

laʻana

E hoʻi ana kēia laʻana mai ka papa chenweiliang_tbl me ka hoʻohana ʻana i ka waiwai kahua chenweiliang_author e like me chenweiliang.com mooolelo o:

MySQL WHERE pauku hōʻike:

<?
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);
?>