25 October, 2023

SQL Server Notes

MERGE

Microsoft Dokumentation

Update rows while using JOIN conditions:

MERGE Flashcards AS target
USING (
  SELECT DISTINCT r.FlashcardsId, r.CategoryId
  FROM Schedule s, RelCategoryFlashcards r, Categories c
  WHERE s.FlashcardId = r.FlashcardId
  AND c.Flag = 1
  AND r.CategoryId = c.Id) AS source
ON target.ID = source.ID
WHEN MATCHED THEN
  UPDATE SET target.NextDate = SYSDATE()
WHEN NOT MATCHED BY source AND target.CatgeoryId = 1
  THEN DELETE;
MERGE Absenz absenz
USING (
  SELECT kak.ID IdKontakt, a.Id IdAbsenz FROM Kunde k
  JOIN Mitarbeiter m on m.IDKunde = k.ID
  JOIN Absenz a on a.IDArbeitnehmer = ka.ID) kunde
ON absenz.ID = k.IdAbsenz
WHEN MATCHED THEN
  UPDATE SET absenz.IDArbeitgeber = kunde.IdKontakt;

DELETE Duplicate Entries

Example to add:

WITH ranked AS (
  SELECT fc.IdTag, prio = ROW_NUMBER() OVER (PARTITION BY fc.IdTag ORDER BY fc.IdTag)
  FROM Flashcards fc
  WHERE fc.IdGroup = 1
)
DELETE FROM ranked WHERE ranked.prio <> 1;

Views

DROP VIEW IF EXISTS dbo.KontaktSuche
GO
IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id('dbo.KontaktSuche') AND OBJECTPROPERTY(id, 'IsView') = 1)
DROP VIEW dbo.KontaktSuche
GO

Show table space usage

This is from a StackOverflow:https://stackoverflow.com/a/7892349/513292

SELECT 
    t.NAME AS TableName,
    s.Name AS SchemaName,
    p.rows,
    SUM(a.total_pages) * 8 AS TotalSpaceKB, 
    CAST(ROUND(((SUM(a.total_pages) * 8) / 1024.00), 2) AS NUMERIC(36, 2)) AS TotalSpaceMB,
    SUM(a.used_pages) * 8 AS UsedSpaceKB, 
    CAST(ROUND(((SUM(a.used_pages) * 8) / 1024.00), 2) AS NUMERIC(36, 2)) AS UsedSpaceMB, 
    (SUM(a.total_pages) - SUM(a.used_pages)) * 8 AS UnusedSpaceKB,
    CAST(ROUND(((SUM(a.total_pages) - SUM(a.used_pages)) * 8) / 1024.00, 2) AS NUMERIC(36, 2)) AS UnusedSpaceMB
FROM 
    sys.tables t
INNER JOIN      
    sys.indexes i ON t.OBJECT_ID = i.object_id
INNER JOIN 
    sys.partitions p ON i.object_id = p.OBJECT_ID AND i.index_id = p.index_id
INNER JOIN 
    sys.allocation_units a ON p.partition_id = a.container_id
LEFT OUTER JOIN 
    sys.schemas s ON t.schema_id = s.schema_id
WHERE 
    t.NAME NOT LIKE 'dt%' 
    AND t.is_ms_shipped = 0
    AND i.OBJECT_ID > 255 
GROUP BY 
    t.Name, s.Name, p.Rows
ORDER BY 
    TotalSpaceMB DESC, t.Name