SQL server trigger concat - sql

Question

I'm trying to write a SQL Server trigger that concats 3 columns, but inserts a string in place of the third column based on a condition.
For example when col 1 is inserted concat col 1, col 2 and col 3. But when col 3 = 'DR' concat Drive or col 3 = 'ST' concat Street etc.
I can write the trigger for all 3 columns, but having trouble with the conditional.
CREATE TRIGGER updateAddress
ON [ARCHIVENEW].dbo.a11
AFTER UPDATE
AS BEGIN
SET NOCOUNT ON;
IF UPDATE(STRNAME)
SELECT CASE
WHEN a11.STRTYPE = 'DR' THEN dbo.a11.STRFNAME = cast(dbo.a11.STRADDLF as varchar(2)) + ' ' + STRNAME + ' ' + 'Drive'
WHEN a11.STRTYPE = 'RP' THEN dbo.a11.STRFNAME = cast(dbo.a11.STRADDLF as varchar(2)) + ' ' + STRNAME + ' ' + 'Ramp'
WHEN a11.STRTYPE = 'EX' THEN dbo.a11.STRFNAME = cast(dbo.a11.STRADDLF as varchar(2)) + ' ' + dbo.a11.STRNAME + ' ' + 'Express Way'
ELSE dbo.a11.STRFNAME = cast(dbo.a11.STRADDLF as varchar(2)) + ' ' + dbo.a11.STRNAME
END
Sorry it took a few days to get back to this and add the code sample. I'm getting a syntax error near the '=' where I try and set my STRFNAME to the concatenated string. To clarify further, col1 is "1234" col2 is "Main" and col3 is "ST". When a row is inserted I'd like col4 to say "1234 Main Street".

Answer 1

Sample table:
CREATE TABLE dbo.TestTable(
Id INT IDENTITY(1,1) PRIMARY KEY
ColA VARCHAR(50),
ColB VARCHAR(50),
ColC VARCHAR(50),
ColD VARCHAR(50)
);
This trigger concats values of ColA, ColB for ColC and validates ColB value for ColD.
CREATE TRIGGER TestTable_UpdateTwoColumns
ON dbo.TestTable
AFTER INSERT,UPDATE
AS
BEGIN
SET NOCOUNT ON;
IF UPDATE(ColA)
BEGIN
UPDATE dbo.TestTable
SET ColC=new.ColA + new.ColB
FROM INSERTED new
END
IF UPDATE(ColB)
BEGIN
UPDATE dbo.TestTable
SET ColD=CASE new.ColB WHEN 'DR' THEN 'Drive' WHEN 'ST' THEN
'Street' END
FROM INSERTED new
END
END
Thanks,

Answer 2

You cannot change a table while the INSERT trigger is firing. You can, however, create a trigger before inserting the record.
CREATE TRIGGER emplog_update AFTER UPDATE ON emp
FOR EACH ROW
INSERT INTO emplog (id, lastnmae, firstname, . . .)
select NEW.id,NEW.lastname,NEW.firstname,NEW.gender,NEW.dob,NEW.marital,NEW.SSN,'U',NULL,USER(),
concat_ws(',',
(case when new.id <> old.id then 'id' end),
(case when new.lastname <> old.lastname then 'lastname' end),
(case when new.firstname <> old.firstname then 'firstname' end),
. . .
);

Answer 3

If your motto is insert into third column, good to use computed column. Here is an example. But as in my comment on question, I did not understand, how col3 value comes?
For this, I used col4 to get the proper result, also in computed column define, it not take reference of own.
CREATE TABLE dbo.Products
(
ProductID int IDENTITY (1,1) NOT NULL
, col1 varchar(50)
, col2 varchar(50)
, col3 varchar(50)
, col4 AS case col3 when 'DR' then 'Drive' when 'ST' then 'Street' else col1 + col2 end
--while computed column define, you can use all other column, except own.
);
-- Insert values into the table.
INSERT INTO dbo.Products (col1, col2,col3)
VALUES ('a', 'a1','a2'), ('b', 'b1', 'DR'), ('c', 'c1', 'ST'), ('d', 'd1', 'd2');
-- Display the rows in the table.
SELECT ProductID, col1, col2, col3, col4
FROM dbo.Products;
select * from products
drop table products