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 CommentsProcedural SQL (PSQL) Statements 

The FROM clause

The FROM clause specifies the source(s) from which the data are to be retrieved.In its simplest form, this is a single table or view.However, the source can also be a selectable stored procedure, a derived table, or a common table expression.Multiple sources can be combined using various types of joins.

This section focuses on single-source selects.Joins are discussed in a following section.

Syntax
SELECT
  ...
  FROM <table-reference> [, <table-reference> ...]
  [...]

<table-reference> ::= <table-primary> | <joined-table>

<table-primary> ::=
    <table-or-query-name> [[AS] correlation-name]
  | [LATERAL] <derived-table> [<correlation-or-recognition>]
  | <parenthesized-joined-table>

<table-or-query-name> ::=
    table-name
  | query-name
  | [package-name.]procedure-name [(<procedure-args>)]

<procedure-args> ::= <value-expression [, <value-expression> ...]

<derived-table> ::= (<query-expression>)

<correlation-or-recognition> ::=
  [AS] correlation-name [(<column-name-list>)]

<column-name-list> ::= column-name [, column-name ...]
Table 1. Arguments for the FROM Clause
Argument Description

table-name

Name of a table or view

query-name

Name of a CTE

package-name

Name of a package

procedure-name

Name of a selectable stored procedure

procedure-args

Selectable stored procedure arguments

derived-table

Derived table query expression

correlation-name

The alias of a data source (table, view, procedure, CTE, derived table)

column-name

Name or alias for a column in a relation, CTE or derived table

Selecting FROM a table or view

When selecting from a single table or view, the FROM clause requires nothing more than the name.An alias may be useful or even necessary if there are subqueries that refer to the main select statement (as they often do — subqueries like this are called correlated subqueries).