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MS-SQL: Insert value only if value not present

Posted on 2004-09-25
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Last Modified: 2012-05-05
I'm trying to be more selective on my row inserts. Probably better than deleting duplicate rows later. So, I have the following syntax which is incorrect, but you'll get the idea I'm attempting.........

INSERT INTO table1 (col_1) VALUES ( '64.39.21.112' )
(select col_1, count(*) as counted
from table1
where col_1 value not exist)
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Question by:kvnsdr
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7 Comments
 
LVL 15

Expert Comment

by:jdlambert1
ID: 12152269
INSERT INTO table1 (col_1)
SELECT '64.39.21.112'
WHERE NOT EXISTS (SELECT '64.39.21.112' FROM table1)
0
 
LVL 6

Expert Comment

by:jchopde
ID: 12153449
DECLARE @myValue varchar(20)
SET @myValue = '64.39.21.112'

IF NOT EXISTS (SELECT 1 FROM table1 WHERE col_1 = @myValue)
  INSERT INTO table1 (col_1) values (@myValue)
ELSE
  --whatever you want to do if the record exists already
  --No need for ELSE if you want to do nothing when the record exists

Alternatively, slightly alter jdlambert1's solution above as follows --

DECLARE @myValue varchar(20)
SET @myValue = '64.39.21.112'

INSERT INTO table1 (col_1)
SELECT @myValue
FROM table1
WHERE NOT EXISTS (SELECT 1 FROM table1 WHERE col_1 = @myValue)
0
 
LVL 7

Expert Comment

by:FDzjuba
ID: 12154285
you can use trigger, i have made it as DELETE from inserted just because i don't know what columns you want to validate


create INS_table1 on table1
INSTEAD OF INSERT
as
DELETE inserted
FROM (SELECT * FROM authors)

insert into table1
SELECT * FROM inserted
0
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LVL 7

Expert Comment

by:FDzjuba
ID: 12154297
sorry, got the above wrong, trigger would be like

CREATE TRIGGER INS_table1 on table1
INSTEAD OF INSERT
as

INSERT INTO table1
SELECT * FROM inserted WHERE NOT EXISTS (SELECT * FROM table1 INNER JOIN inserted ON inserted.col1=table1.col1)

with this trigger you will always avoid inserting dublicated col1
0
 
LVL 1

Author Comment

by:kvnsdr
ID: 12155192
The current code needs to be amended somehow. It inserts string values into the table. I use C# .NET.........

INSERT INTO table1 (col_1) VALUES ( ' " + str_col_1.Trim() + " ' ) ";
0
 
LVL 6

Accepted Solution

by:
jchopde earned 125 total points
ID: 12155310
I do not claim to know C# at all but based on what your wrote above, use the following --

"IF NOT EXISTS (SELECT 1 FROM table1 WHERE col_1 = '" + str_col_1.Trim() + "')  INSERT INTO table1 (col_1) values ('" + str_col_1.Trim() + " ' ) ";
0
 
LVL 15

Expert Comment

by:jdlambert1
ID: 12155675
"IF NOT EXISTS... INSERT INTO..." is two separate commands. While it can work, it's better to use a single command:

If you have string variables named "IP" & "sql":

IP = "64.39.21.112"
sql = "INSERT INTO table1 (col_1) SELECT '" + IP + "'WHERE NOT EXISTS (SELECT '" + IP + "' FROM table1)"
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