All columns must be either typed to an XML schema or untyped. For more information, see Precision, Scale, and Length (Transact-SQL).Ĭolumns of the xml data type must be equal. When the types are the same but differ in precision, scale, or length, the result is based on the same rules for combining expressions. When data types differ, the resulting data type is determined based on the rules for data type precedence. The definitions of the columns that are part of a UNION operation don't have to be the same, but they must be compatible through implicit conversion. Is a query specification or query expression that returns data to be combined with the data from another query specification or query expression. To view Transact-SQL syntax for SQL Server 2014 and earlier, see Previous versions documentation. The number and the order of the columns must be the same in all queries. ![]() The following are basic rules for combining the result sets of two queries by using UNION: A JOIN compares columns from two tables, to create result rows composed of columns from two tables.But a UNION does not create individual rows from columns gathered from two tables. A UNION concatenates result sets from two queries. ![]() You control whether the result set includes duplicate rows:Ī UNION operation is different from a JOIN: Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) SQL Endpoint in Microsoft Fabric Warehouse in Microsoft FabricĬoncatenates the results of two queries into a single result set.
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