SQL UPDATE all values in a field with appended string CONCAT not working

问题

Here is what I want to do:

current table:

+----+-------------+  
| id | data        |  
+----+-------------+  
|  1 | max         |  
|  2 | linda       |  
|  3 | sam         |  
|  4 | henry       |  
+----+-------------+

Mystery Query ( something like "UPDATE table SET data = CONCAT(data, 'a')" )

resulting table:

+----+-------------+  
| id | data        |  
+----+-------------+  
|  1 | maxa        |  
|  2 | lindaa      |  
|  3 | sama        |  
|  4 | henrya      |  
+----+-------------+

thats it! I just need to do it in a single query, but can't seem to find a way. I am using mySQL on bluehost (I think its version 4.1)

Thanks everyone.

回答1:

That's pretty much all you need:

mysql> select * from t;
+------+-------+
| id   | data  |
+------+-------+
|    1 | max   |
|    2 | linda |
|    3 | sam   |
|    4 | henry |
+------+-------+
4 rows in set (0.02 sec)

mysql> update t set data=concat(data, 'a');
Query OK, 4 rows affected (0.01 sec)
Rows matched: 4  Changed: 4  Warnings: 0

mysql> select * from t;
+------+--------+
| id   | data   |
+------+--------+
|    1 | maxa   |
|    2 | lindaa |
|    3 | sama   |
|    4 | henrya |
+------+--------+
4 rows in set (0.00 sec)

Not sure why you'd be having trouble, though I am testing this on 5.1.41

回答2:

CONCAT with a null value returns null, so the easiest solution is:

UPDATE myTable SET spares = IFNULL (CONCAT( spares , "string" ), "string")

回答3:

UPDATE mytable SET spares = CONCAT(spares, ',', '818') WHERE id = 1

not working for me.

spares is NULL by default but its varchar

回答4:

Solved it. Turns out the column had a limited set of characters it would accept, changed it, and now the query works fine.

回答5:

UPDATE 
    myTable
SET 
    col = CONCAT( col , "string" )

Could not work it out. The request syntax was correct, but "0 line affected" when executed.

The solution was :

UPDATE 
    myTable 
SET 
    col = CONCAT( myTable.col , "string" )

That one worked.

回答6:

convert the NULL values with empty string by wrapping it in COALESCE

"UPDATE table SET data = CONCAT(COALESCE(`data`,''), 'a')"

Use CONCAT_WS instead:

"UPDATE table SET data = CONCAT_WS(',',data, 'a')"

回答7:

You can do this:

Update myTable
SET spares = (SELECT CASE WHEN spares IS NULL THEN '' ELSE spares END AS spares WHERE id = 1) + 'some text'
WHERE id = 1

field = field + value does not work when field is null.

来源：https://stackoverflow.com/questions/4128335/sql-update-all-values-in-a-field-with-appended-string-concat-not-working

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sql

mysql

concatenation

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