I'm trying to write an update statement that checks if an element exists in an XML column, and updating it's value if it exists. If not it will then insert the value as a new element.
Something like:
UPDATE Table
SET xmlCol =
case
when xmlCol.exist('element') = 1
then xmlCol.modify('replace value of blah')
else xmlCol.modify('insert blah')
end
where whatever
Am I going about this the wrong way?
The modify() method of the xml data type can only be used in the SET clause of an UPDATE statement.
It's probably simplest to do it in two statements.
UPDATE Table
SET xmlCol.modify('replace value of /blah')
WHERE xmlCol.exist('/blah') = 1;
UPDATE Table
SET xmlCol.modify('insert /blah')
WHERE xmlCol.exist('/blah') = 0;
Related
update autos
set autos.risico = #tbldeelnames.risico
Get an error on #tbldeelnames
Scalar value refers to a single value.
UPDATE a
SET a.riscio = t.risico
FROM #autos a
JOIN #tbldeelnames t on a.key = t.key
OR:
DECLARE #risico INT = 0;
[Do stuff to find value of risico and set it]
UPDATE Autos SET risico = #risico
Your update statement assumes there's only one autos.risico and only one #tbldeelname.risico, which means you don't need tables to hold the value(s), and your update statement makes no sense in that context.
If your #tbldeelnames contains more than one record, then you need to specify WHICH record to use from #tbldeelnames. And, which record from #autos to update, otherwise all records in #autos will be updated with the value from the chosen record in #tbldeellnames.
I have a stored procedure that uses a simple UPDATE with some variables passed to it. But I don't want to update those fields when their variables aren't null. This is essentially what my statement looks like.
UPDATE myTable
SET myColumn = #myColumn,
mColumn1 = #myColumn1
WHERE myColumn2 = #myColumn2
Is there anyway to apply some conditional logic within the SET? I have around 10 fields that need to be checked, so I wouldn't want to do an update per field or something like that.
Any ideas?
COALESCE is your friend. It returns its first non-NULL argument. I'm not actually sure from your narrative which way around you want things, it's either:
UPDATE myTable
SET myColumn = COALESCE(myColumn,#myColumn),
mColumn1 = COALESCE(myColumn1,#myColumn1)
WHERE myColumn2 = #myColumn2
Which keeps the current column's value if the column's not null, or
UPDATE myTable
SET myColumn = COALESCE(#myColumn,myColumn),
mColumn1 = COALESCE(#myColumn1,myColumn1)
WHERE myColumn2 = #myColumn2
Which keeps the current column's value if the variable is null.
Try to use coalesce function as below
UPDATE myTable
SET myColumn = coalesce(myColumn,#myColumn),
mColumn1 = coalesce(mColumn1,#myColumn1)
WHERE myColumn2 = #myColumn2
Above code updates your columns only when they are null. If they are not null the code sets the same value stored in the columns.
ISNULL ( variable , in case of null default value)
INFO
I have a merge statement that should update or insert a single record always. I want to remember the ID of that statement in a variable. It looks like this:
DECLARE #int int
MERGE dbo.table AS A
USING (SELECT 'stringtomatch' AS string) AS B ON B.string= A.string
WHEN MATCHED THEN
UPDATE SET somecolumn = 'something'
WHEN NOT MATCHED THEN
INSERT
VALUES ('stringtomatch',
'something')
OUTPUT #int = inserted.ID;
Now this doesen't work because you can't set #int in the output clause this way. I know I could create a temptable and use INTO #temptable in the output. But since I know it's always a single record I want to have the ID in a INT variable.
Is this even possible? Or am I forced to use a table variable.
How?
No, you have to use a table variable with OUTPUT
However, you can do this...
...
WHEN MATCHED THEN
UPDATE
SET
#int = ID,
somecolumn = 'something'
WHEN NOT MATCHED THEN
INSERT
VALUES ('stringtomatch',
'something');
SET #int = ISNULL(#int, SCOPE_IDENTITY());
The "assign in UPDATE" has been a valid syntax for SQL Server for a long time. See MERGE on MSDN too. Both say this:
...<set_clause>::=
SET
...
#variable=expression
I use this code to check if an element of the new entry is equal to an element of previously inserted data.
CREATE TRIGGER trig1 ON Table1
AFTER INSERT
AS
DECLARE trigcursor CURSOR FOR
SELECT Name FROM INSERTED
DECLARE #Name1 varchar(80)
OPEN trigcursor;
FETCH NEXT FROM trigcursor INTO #Name1
WHILE ##FETCH_STATUS = 0
BEGIN
IF EXISTS(SELECT * FROM Table1 WHERE Name= #Name1)
BEGIN
...
END
FETCH NEXT FROM trigcursor INTO #Name1
END
The problem is that for some reason the new entry exists also in the table Table1, not only in INSERTED. So the condition is always true. Can you help me why this happens? Is there a way to retrieve only the initial table without the new entry in it? Thanks!
Your trigger is AFTER INSERT on table Table1. It should be BEFORE INSERT if you expect not to find the record in the table.
Alternative: use INSTEAD OF INSERT trigger.
OR
Add another column that accepts null. Make it a number column so that it will be fast. Do not insert any value in it on the insert. Then, in the AFTER INSERT TRIGGER, the rows that have that column empty are the new ones. The ones that have the column filled with something are the old ones.
Then update empty columns with value.
eg: add column mark
After insert, look for the name:
SELECT * FROM Table1 WHERE Name= #Name1 and mark is not null
Once you found out whether or not it existed before, update everything with something:
update table1 set mark = 1 where mark is null
If there's:
IF UPDATE (col1)
...in the SQL server trigger on a table, does it return true only if col1 has been changed or been updated?
I have a regular update query like
UPDATE table-name
SET col1 = 'x',
col2 = 'y'
WHERE id = 999
Now what my concern is if the "col1" was 'x' previously then again we updated it to 'x'
would IF UPDATE ("col1") trigger return True or not?
I am facing this problem as my save query is generic for all columns, but when I add this condition it returns True even if it's not changed...So I am concerned what to do in this case if I want to add condition like that?
It returns true if a column was updated. An update means that the query has SET the value of the column. Whether the previous value was the same as the new value is largely irelevant.
UPDATE table SET col = col
it's an update.
UPDATE table SET col = 99
when the col already had value 99 also it's an update.
Within the trigger, you have access to two internal tables that may help. The 'inserted' table includes the new version of each affected row, The 'deleted' table includes the original version of each row. You can compare the values in these tables to see if your field value was actually changed.
Here's a quick way to scan the rows to see if ANY column changed before deciding to run the contents of a trigger. This can be useful for example when you want to write a history record, but you don't want to do it if nothing really changed.
We use this all the time in ETL importing processes where we may re-import data but if nothing really changed in the source file we don't want to create a new history record.
CREATE TRIGGER [dbo].[TR_my_table_create_history]
ON [dbo].[my_table] FOR UPDATE AS
BEGIN
--
-- Insert the old data row if any column data changed
--
INSERT INTO [my_table_history]
SELECT d.*
FROM deleted d
INNER JOIN inserted i ON i.[id] = d.[id]
--
-- Use INTERSECT to see if anything REALLY changed
--
WHERE NOT EXISTS( SELECT i.* INTERSECT SELECT d.* )
END
Note that this particular trigger assumes that your source table (the one triggering the trigger) and the history table have identical column layouts.
What you do is check for different values in the inserted and deleted tables rather than use updated() (Don't forget to account for nulls). Or you could stop doing unneeded updates.
Trigger:
CREATE TRIGGER boo ON status2 FOR UPDATE AS
IF UPDATE (id)
BEGIN
SELECT 'DETECT';
END;
Usage:
UPDATE status2 SET name = 'K' WHERE name= 'T' --no action
UPDATE status2 SET name = 'T' ,id= 8 WHERE name= 'K' --detect
To shortcut the "No actual update" case, you need also check at the beginning whether your query affected any rows at all:
set nocount on; -- this must be the first statement!
if not exists (select 1 from inserted) and not exists (select 1 from deleted)
return;
SET NOCOUNT ON;
declare #countTemp int
select #countTemp = Count (*) from (
select City,PostCode,Street,CountryId,Address1 from Deleted
union
select City,PostCode,Street,CountryId,Address1 from Inserted
) tempTable
IF ( #countTemp > 1 )
Begin
-- Your Code goes Here
End
-- if any of these "City,PostCode,Street,CountryId,Address1" got updated then trigger
-- will work in " IF ( #countTemp > 1 ) " Code)
This worked for me
DECLARE #LongDescDirty bit = 0
Declare #old varchar(4000) = (SELECT LongDescription from deleted)
Declare #new varchar(4000) = (SELECT LongDescription from inserted)
if (#old <> #new)
BEGIN
SET #LongDescDirty = 1
END
Update table
Set LongDescUpdated = #LongDescUpdated
.....