Join constructs

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USoft supports a variety of join constructs to express SQL SELECT statements that refer to more than 1 table instance.

Before a statement is sent to the RDBMS, USoft converts constructs with JOIN to standard join syntax (shown at the beginning of this help topic).

USoft recommends that you standardise :

for inner joins, which will be the overwhelming majority of cases, use standard syntax;

for outer joins, use the (+) syntax.

In all code examples in this help topic, table represents a required table name for which you can optionally supply an alias. Aliases are recommended - all the examples use aliases. Each occurrence of table represents not a table as such, but a table instance: within a single join statement, you can have multiple table occurrences for the same table, resulting in multiple table instances of that table. Table name in USoft may refer to a database table, a Logical View, or a component table.



collapseInner join: standard syntax
collapseInner join: [INNER] JOIN syntax
collapseOuter join: (+) syntax
collapseOuter join: LEFT/RIGHT [OUTER] JOIN syntax
collapseOuter join: *= syntax
collapseCross join



See also

Queries and subqueries

DML statements

Table aliases

Transaction control statements

SQL and the Rules Engine