Understanding Combined Queries
Most SQL queries contain a single SELECT statement that returns data from one or more tables. SQL also enables you to perform multiple queries (multiple SELECT statements) and return the results as a single query result set. These combined queries are usually known as unions or compound queries.
There are basically two scenarios in which you'd use combined queries:
To return similarly structured data from different tables in a single query
To perform multiple queries against a single table returning the data as one query
 | Combining Queries and Multiple WHERE Conditions For the most part, combining two queries to the ... |
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