I'm trying to migrate a MySQL-based app over to Microsoft SQL Server 2005 (not by choice, but that's life).
In the original app, we used almost entirely ANSI-SQL compliant statements, with one significant exception -- we used MySQL's group_concat
function fairly frequently.
group_concat
, by the way, does this: given a table of, say, employee names and projects...
SELECT empName, projID FROM project_members;
returns:
ANDY | A100
ANDY | B391
ANDY | X010
TOM | A100
TOM | A510
... and here's what you get with group_concat:
SELECT
empName, group_concat(projID SEPARATOR ' / ')
FROM
project_members
GROUP BY
empName;
returns:
ANDY | A100 / B391 / X010
TOM | A100 / A510
So what I'd like to know is: Is it possible to write, say, a user-defined function in SQL Server which emulates the functionality of group_concat
?
I have almost no experience using UDFs, stored procedures, or anything like that, just straight-up SQL, so please err on the side of too much explanation :)
No REAL easy way to do this. Lots of ideas out there, though.
SELECT table_name, LEFT(column_names , LEN(column_names )-1) AS column_names
FROM information_schema.columns AS extern
CROSS APPLY
(
SELECT column_name + ','
FROM information_schema.columns AS intern
WHERE extern.table_name = intern.table_name
FOR XML PATH('')
) pre_trimmed (column_names)
GROUP BY table_name, column_names;
Or a version that works correctly if the data might contain characters such as <
WITH extern
AS (SELECT DISTINCT table_name
FROM INFORMATION_SCHEMA.COLUMNS)
SELECT table_name,
LEFT(y.column_names, LEN(y.column_names) - 1) AS column_names
FROM extern
CROSS APPLY (SELECT column_name + ','
FROM INFORMATION_SCHEMA.COLUMNS AS intern
WHERE extern.table_name = intern.table_name
FOR XML PATH(''), TYPE) x (column_names)
CROSS APPLY (SELECT x.column_names.value('.', 'NVARCHAR(MAX)')) y(column_names)