#056 Combine queries by union in Azure SQL

This T-SQL code uses the UNION clause to combine the results of two different queries, one for the table [f].[ Mercado_Exportacao] and another for table [f]. [Mercado_Importacao]. I'll explain each part of the code

1. Union Part One:

   SELECT [CO_ANO], [

   CO_MES], [KG_LIQUIDO], 'Export' AS TYPE
   FROM [f]. [Mercado_Exportacao]
   

   • SELECT: Indicates that the next part of the code will specify which columns will be returned in the query.
   [CO_ANO], [CO_MES
   • ], [KG_LIQUIDO]: Select the "CO_ANO", "CO_MES", and "KG_LIQUIDO" columns.
   AS TYPE '
   • Export': Adds an additional column called 'TYPE' with the constant 'Export' value for each resulting row in the table [f]. [Mercado_Exportacao].
UNION:

2. UNION Operator

   • : Combines the results of two queries, eliminating duplicates. UNION requires queries to have the same number of columns, with matching data types.

3. Union Part Two:

   SELECT [CO_ANO], [

   CO_MES], [KG_LIQUIDO], 'Import' AS TYPE
   FROM [f]. [Mercado_Importacao]
   

   • SELECT: Indicates that the next part of the code will specify which columns will be returned in the query.
   [CO_ANO], [CO_MES
   • ], [KG_LIQUIDO]: Select the "CO_ANO", "CO_MES", and "KG_LIQUIDO" columns.
   AS TYPE '
   • Import': Adds an additional column called 'TYPE' with the constant 'Import' value for each resulting row of the table [f]. [Mercado_Importacao].

The final result of the query is the combination of the results of the two parts, where each row will have the columns "CO_ANO", "CO_MES", "KG_LIQUIDO" and "TYPE". The "TYPE" column indicates whether the data is export-related or import-related. This is useful when you need to group or analyze data from different related tables.