Difference between Join and Union
Join
By using joins, you can retrieve data from two or more tables based on logical relationships between the tables.
Union
The UNION set operator is used for combining data from two tables which have columns with the same data type. When a UNION is performed the data from both tables will be collected in a single column having the same data type.
Difference between Join and Union
Join
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Union
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Only primary key & foreign key column & data types of both tables must be same
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All column & data types of both tables must be same
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Selects columns from 2 or more tables
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Selects rows from two or more
tables
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Generally used to combine rows from multiple tables
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Generally used to merge two or more tables
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SELECT a.Column1, b.Column2 FROM TableA a INNER JOIN TableB b ON a.id = b.id
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SELECT 1 AS [Column1], 2 AS [Column2]
UNION
SELECT 3 AS [Column1], 4 AS [Column2]
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