Queries and subqueries

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A query is a SQL statement that retrieves data from an RDBMS.

In SQL generally, you may retrieve data :

For presentation to humans (on a screen, in a report...) , or for further processing by software. In this case, the query is performed by a SELECT statement.

As input for a further query (SELECT) or for a data manipulation operation (INSERT, UPDATE, DELETE). In this case, the query is performed by a subquery.

In USoft specifically, queries are used additionally for other purposes. Most importantly, query statements define restrictive table constraints in order to perform restrictive data integrity checks.

 

 

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See also

Join constructs

DML statements

Table aliases

Transaction control statements

Set operators

Method invocation statements