Syntax error with IF EXISTS UPDATE ELSE INSERT

问题

I'm using MySQL 5.1 hosted at my ISP. This is my query

mysql_query("
IF EXISTS(SELECT * FROM licensing_active WHERE title_1='$title_1') THEN
    BEGIN
        UPDATE licensing_active SET time='$time' WHERE title_1='$title_1')
    END ELSE BEGIN
        INSERT INTO licensing_active(title_1) VALUES('$title_1')
    END   
") or die(mysql_error());

The error is

... check the manual that corresponds to your MySQL server version for the right syntax to use near 'IF EXISTS(SELECT * FROM licensing_active WHERE title_1='Title1') THEN ' at line 1

My actual task involves

WHERE title_1='$title_1' AND title_2='$title_2' AND version='$version' ...ETC...

but I have reduced it down to make things simpler for my problem solving

In my searches on this, I keep seeing references to 'ON DUPLICATE KEY UPDATE', but don't know what to do with that.

回答1:

Here is a simple and easy solution, try it.

$result = mysql_query("SELECT * FROM licensing_active WHERE title_1 ='$title_1' ");

if( mysql_num_rows($result) > 0) {
    mysql_query("UPDATE licensing_active SET time = '$time' WHERE title_1 = '$title_1' ");
}
else
{
    mysql_query("INSERT INTO licensing_active (title_1) VALUES ('$title_1') ");
}

Note: Though this question is from 2012, keep in mind that mysql_* functions are no longer available since PHP 7.

回答2:

This should do the trick for you:

insert into 
    licensing_active (title_1, time) 
    VALUES('$title_1', '$time') 
    on duplicate key 
        update set time='$time'

This is assuming that title_1 is a unique column (enforced by the database) in your table.

The way that insert... on duplicate works is it tries to insert a new row first, but if the insert is rejected because a key stops it, it will allow you to update certain fields instead.

回答3:

The syntax of your query is wrong. Checkout http://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html

Use the on duplicate key syntax to achieve the result you want. See http://dev.mysql.com/doc/refman/5.0/en/insert-select.html

来源：https://stackoverflow.com/questions/12436602/syntax-error-with-if-exists-update-else-insert

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