Ungayisebenzisa kanjani i-MySQL lapho isitatimende? lapho isigatshana se-syntax enemibandela eminingi

MySQL databaseIndlela yokusebenzisa lapho isitatimende? lapho isigatshana se-syntax enemibandela eminingi

MySQL LAPHO isigatshana

Siyazi ukusebenzisa isitatimende se-SQL KHETHA ukufunda idatha kusuka kuthebula le-MySQL.

Ukuze ukhethe idatha etafuleni, engeza isigatshana esithi LAPHO esitatimendeni esithi KHETHA.

uhlelo lolimi

Okulandelayo i-syntax evamile yesitatimende se-SQL KHETHA ukufunda idatha kusuka kuthebula ledatha usebenzisa isigatshana esithi LAPHO:

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

• Ungasebenzisa ithebula elilodwa noma amaningi esitatimendeni sombuzo, usebenzisa okhefana phakathi kwamathebula, Hlukanisa, futhi usebenzise isitatimende esithi WHERE ukuze usethe izimo zombuzo.
• Ungacacisa noma yimuphi umbandela esigatshaneni esithi LAPHO.
• Ungacacisa umbandela owodwa noma ngaphezulu usebenzisa KANYE noma NOMA.
• Isigatshana esithi LAPHO singasetshenziswa futhi nemiyalo ye-SQL's DELETE noma UPDATE.
• Isigatshana esithi LAPHO sifana nesithi uma isimo ezilimini zenqubo, futhi sifunda idatha eshiwo ngokwenani lenkundla kuthebula le-MySQL.

Okulandelayo uhlu lwama-opharetha angasetshenziswa esigatshaneni esithi LAPHO.

Izibonelo ezisethebulani elingezansi zithatha ngokuthi u-A ngu-10 no-B ngu-20

Isigatshana esithi LAPHO siwusizo kakhulu uma sifuna ukufunda idatha eshiwo kuthebula ledatha le-MySQL.

Ukusebenzisa ukhiye oyinhloko njengombuzo onemibandela esigatshaneni esithi LAPHO kushesha kakhulu.

Uma imibandela enikeziwe ingenawo amarekhodi afanayo kuthebula, umbuzo awubuyisi idatha.

funda idatha kusuka kumyalo womyalo

Sizosebenzisa isigatshana esithi WHERE esitatimendeni esithi KHETHA ukuze sifunde idatha kuthebula ledatha le-MySQL elithi chenweiliang_tbl:

Isibonelo

Isibonelo esilandelayo sizofunda wonke amarekhodi kuthebula le-chenweiliang_tbl lapho inani lenkambu ye-chenweiliang_author lingu-Sanjay:

Ukuqhathaniswa kweyunithi yezinhlamvu ku-MySQL's WHERE isigatshana akunandaba.Ungasebenzisa igama elingukhiye IBHAYIBHELI ukuze ucacise ukuthi ukuqhathanisa kweyunithi yezinhlamvu kokuthi LAPHO isigatshana sibucayi kakhulu.

Isibonelo esilandelayo:

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)

esetshenziswe esibonelweni IBHASARI igama elingukhiye, liyazwela, ngakho chenweiliang_author='chenweiliang.com' Umbandela wombuzo akuyona idatha.

Funda idatha usebenzisa umbhalo we-PHP

Ungasebenzisa umsebenzi we-PHP mysqli_query() kanye nomyalo ofanayo we-SQL KHETHA onesigatshana esithi LAPHO ukuze uthole idatha.

Lo msebenzi usetshenziselwa ukukhipha imiyalo ye-SQL bese ukhipha yonke idatha ebuziwe ngomsebenzi we-PHP mysqli_fetch_array().

Isibonelo

Isibonelo esilandelayo sizobuya kuthebula le-chenweiliang_tbl kusetshenziswa inani lenkambu ye-chenweiliang_author njenge chenweiliang.com irekhodi la:

MySQL LAPHO ukuhlolwa kwesigatshana:

<?
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);
?>