10. Learn MySQL like clause

 MySQL LIKE Clause

We know that MySQL Use in SQL SELECT Command to read data , At the same time, we can go to SELECT Use in statement WHERE Clause to get the specified record .

 WHERE An equal sign can be used in a clause  =  To set the conditions for obtaining data , Such as "xxxxxx_author = 'XXXXXX.COM'".

But sometimes we need to get xxxxxx_author Field contains "COM" All records of characters , Then we need to WHERE Used in clauses SQL LIKE Clause .

SQL LIKE Use percent sign in Clause  % Character to represent any character , Be similar to UNIX Or an asterisk in a regular expression  *.

If you don't use the percent sign  %, LIKE Clause and equal sign  =  The effect is the same .

grammar

Here are SQL SELECT Statements use LIKE Clause to read data from a data table ：

SELECT field1, field2,...fieldN 
FROM table_name
WHERE field1 LIKE condition1 [AND [OR]] filed2 = 'somevalue'

• You can WHERE Clause to specify any condition .
• You can WHERE Used in clauses LIKE Clause .
• You can use LIKE Clause instead of equal sign  =.
• LIKE Usually with  %  Use together , Similar to a metacharacter search .
• You can use AND perhaps OR Specify one or more conditions .
• You can DELETE or UPDATE Use in command WHERE...LIKE Clause to specify the condition .

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Use... At the command prompt LIKE Clause

Below we will be in SQL SELECT Use in command WHERE...LIKE Clause comes from MySQL Data sheet xxxxxx_tbl Read data from .

example

Here is what we will xxxxxx_tbl Table acquisition xxxxxx_author In the field, use  COM  For all records at the end ：

SQL LIKE sentence ：

mysql> use XXXXXX;
Database changed
mysql> SELECT * from xxxxxx_tbl  WHERE xxxxxx_author LIKE '%COM';
+-----------+---------------+---------------+-----------------+
| xxxxxx_id | xxxxxx_title  | xxxxxx_author | submission_date |
+-----------+---------------+---------------+-----------------+
| 3         |  Study  Java   | XXXXXX.COM    | 2021-11-20      |
| 4         |  Study  Python | XXXXXX.COM    | 2021-11-21      |
+-----------+---------------+---------------+-----------------+
2 rows in set (0.01 sec)

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stay PHP Use in script LIKE Clause

You can use PHP Functional mysqli_query() And the same SQL SELECT close WHERE...LIKE Clause to get data .

This function is used to execute SQL command , And then through PHP function mysqli_fetch_array() To output all the query data .

But if it is DELETE perhaps UPDATE Use in WHERE...LIKE Clause S QL sentence , No need to use mysqli_fetch_array() function .

example

Here's how we use PHP Script in xxxxxx_tbl Read... In table xxxxxx_author In the field, use COM For all records at the end ：

MySQL LIKE Clause test ：

<?php
$dbhost = 'localhost';  // mysql Server host address 
$dbuser = 'root';            // mysql user name 
$dbpass = '123456';          // mysql User name, password 
$conn = mysqli_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
    die(' The connection fails : ' . mysqli_error($conn));
}
//  Set encoding , Prevent Chinese miscoding 
mysqli_query($conn , "set names utf8");
 
$sql = 'SELECT xxxxxx_id, xxxxxx_title, 
        xxxxxx_author, submission_date
        FROM xxxxxx_tbl
        WHERE xxxxxx_author LIKE "%COM"';
 
mysqli_select_db( $conn, 'XXXXXX' );
$retval = mysqli_query( $conn, $sql );
if(! $retval )
{
    die(' Unable to read data : ' . mysqli_error($conn));
}
echo '<h2>xx course  mysqli_fetch_array  test <h2>';
echo '<table border="1"><tr><td> course  ID</td><td> title </td><td> author </td><td> Submission date </td></tr>';
while($row = mysqli_fetch_array($retval, MYSQLI_ASSOC))
{
    echo "<tr><td> {$row['xxxxxx_id']}</td> ".
         "<td>{$row['xxxxxx_title']} </td> ".
         "<td>{$row['xxxxxx_author']} </td> ".
         "<td>{$row['submission_date']} </td> ".
         "</tr>";
}
echo '</table>';
mysqli_close($conn);
?>