Union vs union all SQL server - Union SQL

Union will remove duplicates. Union All does not.

Note:- For union , must have same columns.

example

Union

Select top (select COUNT(*) from CourtApplicationDetails) * From CourtApplicationDetails

union 

Select top ((select COUNT(*) from CourtApplicationDetails)-(1)) * From CourtApplicationDetails

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union all

Select top (select COUNT(*) from CourtApplicationDetails) * From CourtApplicationDetails

union all

Select top ((select COUNT(*) from CourtApplicationDetails)-(1)) * From CourtApplicationDetails