Sql-server – Select using values from another table

sql server

I want to select specific columns from a table, let's say table A. Table B has the names of the names of the columns I would like to select. How would I write a MSSQL query that will use the distinct values from Table B as the column names that I want to query from table A?

Best Answer

Can't you just use the COALESCE function like this?

DECLARE @columnList VARCHAR(MAX), @sql VARCHAR(MAX)
SELECT @columnList = COALESCE(@columnList+',' ,'') + columnName
FROM TableB

SET @sql = 'SELECT ' + @columnList + ' FROM TableA'

EXEC(@sql)

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Sql-server – Select multiple rows from one row based on column values

I'd use UNPIVOT for this unless abr and ubr are both indexed and a relatively low proportion contain the value 1.

(Borrowing JNK's table variable)

SELECT id,
       Edition
FROM @prod
UNPIVOT (V FOR Edition IN (abr,ubr)) AS Unpvt
WHERE V = 1

Sql-server – How to find values from one table missing in another

I assume that you have the following tables:

CREATE TABLE Author(AutorID INT, Name VARCHAR(50));  
CREATE TABLE Article(ArticleID INT, Article VARCHAR(MAX),Author VARCHAR(50));

Now to achieve your result just run the following query:

SELECT DISTINCT Article.Author WHERE Article.Author NOT IN 
(SELECT Author.Name FROM Author) AND Article.Author IS NOT NULL
AND Article.Author != '';

Best Answer

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Sql-server – Select multiple rows from one row based on column values

Sql-server – How to find values from one table missing in another

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