MySql: Wenn Wert existiert UPDATE sonst INSERT

Question

Ich habe etwas Code, der so aussieht. Es gibt auch ein Autoinkrement-Feld in der Tabelle, das ich beibehalten muss (es wird in anderen Tabellen verwendet). Ich möchte diesen Code vereinfachen und optimieren.

$query ="SELECT * FROM models WHERE col1 = 'foo'"; 
$testResult = mysql_query($query) or die('Error, query failed');  

if(mysql_fetch_array($testResult) == NULL){ 
    //insert... 
    $query ="INSERT INTO models (col1, col2, col3) 
    VALUES ('foo', 'bar', 'alph')"; 
    $result = mysql_query($query) or die('Error, query failed'); 
}else{ 
    //update... 
    $query = "UPDATE models 
     SET col1='foo', col2='bar', col3='alph' 
     WHERE col1='foo' AND col2='bar'"; 
     $result = mysql_query($query) or die('Error, query failed');   
} 

Bearbeiten: Die Primärschlüssel-ID ist das Feld, das automatisch inkrementiert wird. Ich möchte das nie ändern. Wenn jedoch ein oder mehrere Felder doppelt vorhanden sind, möchte ich diesen Datensatz aktualisieren.

Answer 1

Wie wäre es ERSETZEN IN:

REPLACE INTO models 
(col1, col2, col3) 
VALUES 
('foo', 'bar', 'alpha') 

Angenommen, col1 ist Ihr Primärschlüssel, wenn bereits eine Zeile mit dem Wert 'foo' existiert, werden die anderen beiden Spalten aktualisiert. Andernfalls wird eine neue Zeile eingefügt.

Answer 2

Sie können versuchen, "INSERT ... ON DUPLICATE KEY UPDATE" verwenden Syntax

http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html

If you specify ON DUPLICATE KEY UPDATE, and a row is inserted that would cause a duplicate value in a UNIQUE index or PRIMARY KEY, an UPDATE of the old row is performed. For example, if column a is declared as UNIQUE and contains the value 1, the following two statements have identical effect: 

INSERT INTO table (a,b,c) VALUES (1,2,3) 
    ON DUPLICATE KEY UPDATE c=c+1; 

UPDATE table SET c=c+1 WHERE a=1; 
The ON DUPLICATE KEY UPDATE clause can contain multiple column assignments, separated by commas. 

With ON DUPLICATE KEY UPDATE, the affected-rows value per row is 1 if the row is inserted as a new row and 2 if an existing row is updated. 

If column b is also unique, the INSERT is equivalent to this UPDATE statement instead: 

UPDATE table SET c=c+1 WHERE a=1 OR b=2 LIMIT 1; 
If a=1 OR b=2 matches several rows, only one row is updated. In general, you should try to avoid using an ON DUPLICATE KEY clause on tables with multiple unique indexes. 

You can use the VALUES(col_name) function in the UPDATE clause to refer to column values from the INSERT portion of the INSERT ... UPDATE statement. In other words, VALUES(col_name) in the UPDATE clause refers to the value of col_name that would be inserted, had no duplicate-key conflict occurred. This function is especially useful in multiple-row inserts. The VALUES() function is meaningful only in INSERT ... UPDATE statements and returns NULL otherwise. Example: 

INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6) 
    ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b); 
That statement is identical to the following two statements: 

INSERT INTO table (a,b,c) VALUES (1,2,3) 
    ON DUPLICATE KEY UPDATE c=3; 
INSERT INTO table (a,b,c) VALUES (4,5,6) 
    ON DUPLICATE KEY UPDATE c=9; 
If a table contains an AUTO_INCREMENT column and INSERT ... UPDATE inserts a row, the LAST_INSERT_ID() function returns the AUTO_INCREMENT value. If the statement updates a row instead, LAST_INSERT_ID() is not meaningful. However, you can work around this by using LAST_INSERT_ID(expr). Suppose that id is the AUTO_INCREMENT column. To make LAST_INSERT_ID() meaningful for updates, insert rows as follows: 

INSERT INTO table (a,b,c) VALUES (1,2,3) 
    ON DUPLICATE KEY UPDATE id=LAST_INSERT_ID(id), c=3; 
The DELAYED option is ignored when you use ON DUPLICATE KEY UPDATE. 

Answer 3

Für MySQL 5.0 + Verwendung: INSERT ON DUPLICATE KEY UPDATE

http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html

Answer 4

Sie müssen Col3 nur bei Duplikaten aktualisieren. Genau darum bitten Sie.

INSERT INTO models (col1, col2, col3) 
VALUES ('foo', 'bar', 'alpha') 
ON DUPLICATE KEY UPDATE col3='alpha';