All, I have a large (unavoidable) dynamic SQL query. Due to the number of fields in the selection criteria the string containing the dynamic SQL is growing over 4000 chars. Now, I understand that there is a 4000 max set for NVARCHAR(MAX)
, but looking at the executed SQL in Server Profiler for the statement
DELARE @SQL NVARCHAR(MAX);
SET @SQL = 'SomeMassiveString > 4000 chars...';
EXEC(@SQL);
GO
Seems to work(!?), for another query that is also large it throws an error which is associated with this 4000 limit(!?), it basically trims all of the SQL after this 4000 limit and leaves me with a syntax error. Despite this in the profiler, it is showing this dynamic SQL query in full(!?).
What exactly is happening here and should I just be converting this @SQL variable to VARCHAR and get on with it?
Thanks for your time.
Ps. It would also be nice to be able to print out more than 4000 chars to look at these big queries. The following are limited to 4000
SELECT CONVERT(XML, @SQL);
PRINT(@SQL);
is there any other cool way?
This question is related to
sql
sql-server
sql-server-2008
variables
string-concatenation
Okay, so if later on down the line the issue is that you have a query that's greater than the allowable size (which may happen if it keeps growing) you're going to have to break it into chunks and execute the string values. So, let's say you have a stored procedure like the following:
CREATE PROCEDURE ExecuteMyHugeQuery
@SQL VARCHAR(MAX) -- 2GB size limit as stated by Martin Smith
AS
BEGIN
-- Now, if the length is greater than some arbitrary value
-- Let's say 2000 for this example
-- Let's chunk it
-- Let's also assume we won't allow anything larger than 8000 total
DECLARE @len INT
SELECT @len = LEN(@SQL)
IF (@len > 8000)
BEGIN
RAISERROR ('The query cannot be larger than 8000 characters total.',
16,
1);
END
-- Let's declare our possible chunks
DECLARE @Chunk1 VARCHAR(2000),
@Chunk2 VARCHAR(2000),
@Chunk3 VARCHAR(2000),
@Chunk4 VARCHAR(2000)
SELECT @Chunk1 = '',
@Chunk2 = '',
@Chunk3 = '',
@Chunk4 = ''
IF (@len > 2000)
BEGIN
-- Let's set the right chunks
-- We already know we need two chunks so let's set the first
SELECT @Chunk1 = SUBSTRING(@SQL, 1, 2000)
-- Let's see if we need three chunks
IF (@len > 4000)
BEGIN
SELECT @Chunk2 = SUBSTRING(@SQL, 2001, 2000)
-- Let's see if we need four chunks
IF (@len > 6000)
BEGIN
SELECT @Chunk3 = SUBSTRING(@SQL, 4001, 2000)
SELECT @Chunk4 = SUBSTRING(@SQL, 6001, (@len - 6001))
END
ELSE
BEGIN
SELECT @Chunk3 = SUBSTRING(@SQL, 4001, (@len - 4001))
END
END
ELSE
BEGIN
SELECT @Chunk2 = SUBSTRING(@SQL, 2001, (@len - 2001))
END
END
-- Alright, now that we've broken it down, let's execute it
EXEC (@Chunk1 + @Chunk2 + @Chunk3 + @Chunk4)
END
declare @p varbinary(max)
set @p = 0x
declare @local table (col text)
SELECT @p = @p + 0x3B + CONVERT(varbinary(100), Email)
FROM tbCarsList
where email <> ''
group by email
order by email
set @p = substring(@p, 2, 100000)
insert @local values(cast(@p as varchar(max)))
select DATALENGTH(col) as collen, col from @local
result collen > 8000, length col value is more than 8000 chars
You mus use nvarchar text too. that's mean you have to simply had a "N" before your massive string and that's it! no limitation anymore
DELARE @SQL NVARCHAR(MAX);
SET @SQL = N'SomeMassiveString > 4000 chars...';
EXEC(@SQL);
GO
The accepted answer helped me but I got tripped up while doing concatenation of varchars involving case statements. I know the OP's question does not involve case statements but I thought this would be helpful to post here for others like me who ended up here while struggling to build long dynamic SQL statements involving case statements.
When using case statements with string concatenation the rules mentioned in the accepted answer apply to each section of the case statement independently.
declare @l_sql varchar(max) = ''
set @l_sql = @l_sql +
case when 1=1 then
--without this correction the result is truncated
--CONVERT(VARCHAR(MAX), '')
+REPLICATE('1', 8000)
+REPLICATE('1', 8000)
end
print len(@l_sql)
Source: Stackoverflow.com