Functions Aggregate:
*List Concatenation
*SUM
*AVG
*Max
*Min
List Concatenation
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List Concatenation aggregates a column or expression by combining the values into a single string for each group. A string to delimit each value (either blank or a comma when omitted) and the order of the values in the result can be specified. While it is not part of the SQL standard, every major relational database vendor supports it in their own way.
MySQL
SELECT ColumnA
, GROUP_CONCAT(ColumnB ORDER BY ColumnB SEPARATOR ',') AS ColumnBs
FROM TableName
GROUP BY ColumnA
ORDER BY ColumnA;Oracle & DB2
SELECT ColumnA
, LISTAGG(ColumnB, ',') WITHIN GROUP (ORDER BY ColumnB) AS ColumnBs
FROM TableName
GROUP BY ColumnA
ORDER BY ColumnA;PostgreSQL
SELECT ColumnA
, STRING_AGG(ColumnB, ',' ORDER BY ColumnB) AS ColumnBs
FROM TableName
GROUP BY ColumnA
ORDER BY ColumnA;SQL Server
SQL Server 2016 and earlier
(CTE included to encourage the DRY principle)
WITH CTE_TableName AS (
SELECT ColumnA, ColumnB
FROM TableName)
SELECT t0.ColumnA
, STUFF((
SELECT ',' + t1.ColumnB
FROM CTE_TableName t1
WHERE t1.ColumnA = t0.ColumnA
ORDER BY t1.ColumnB
FOR XML PATH('')), 1, 1, '') AS ColumnBs
FROM CTE_TableName t0
GROUP BY t0.ColumnA
ORDER BY ColumnA;SQL Server 2017 and SQL Azure
SELECT ColumnA
, STRING_AGG(ColumnB, ',') WITHIN GROUP (ORDER BY ColumnB) AS ColumnBs
FROM TableName
GROUP BY ColumnA
ORDER BY ColumnA;SQLite
without ordering:
SELECT ColumnA
, GROUP_CONCAT(ColumnB, ',') AS ColumnBs
FROM TableName
GROUP BY ColumnA
ORDER BY ColumnA;ordering requires a subquery or CTE:
WITH CTE_TableName AS (
SELECT ColumnA, ColumnB
FROM TableName
ORDER BY ColumnA, ColumnB)
SELECT ColumnA
, GROUP_CONCAT(ColumnB, ',') AS ColumnBs
FROM CTE_TableName
GROUP BY ColumnA
ORDER BY ColumnA;
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