The FROM clause of the SELECT statement lists table objects
from which to retrieve data.
This syntax fragment is part of the SELECT statement.
FROM Clause
|--FROM--------------------------------------------------------->
.-,-----------------------------------------------------------------------------.
| .---------------------------------------------. |
| | .--------------------. | |
V V V (1) | | |
>----+-+---+----| ANSI Tables |------| ANSI Joins |-----+---+--+---+-------------+-+--|
| '-(-' '-)-' |
| .-,-----------------------------------------------. |
| V | |
+-+-| ANSI Tables |--+----+---------------------------------------------+-+-+
| '-| Other Tables |-' | (2) (3) | |
| '-------,--| Informix OUTER Join Clause |-----' |
| (4) |
'-| Lateral derived table |-------------------------------------------------'
ANSI Tables
|--+---+-synonym-------------+----+-------------------+-+-------|
| +-table---------------+ | (5) | |
| +-view----------------+ '-+----+--alias-----' |
| '-ONLY--+-(table )--+-' '-AS-' |
| '-(synonym)-' |
| (2) (6) |
'-----+-| Collection Derived Table |-----+-----------'
| (7) |
'-| Iterator |---------------------'
Other Tables
|--+---external----+-------------------------------------------------+------------------------+--|
| | (5) | |
| '-+----+--alias------+--------------------------+-' |
| '-AS-' | .-,--------------. | |
| | V | | |
| '-(----derived_column-+--)-' |
| (8) (9) |
+-(------| Collection Subquery |--)--------------------------------------------------------+
+-(--subquery--)---------------------------------------------------------------------------+
| .-,--------------. |
| (5) V | |
'-+-+-table---+-----------------------------+--+----+--alias------(----derived_column-+--)-'
| +-view----+ | '-AS-'
| '-synonym-' |
| (2) (10) (11) |
'-------ONLY--(-------+-table---+--)------'
'-synonym-'
Notes:
- See ANSI Joins
- Informix extension
- See Informix-Extension Outer Joins
- See Lateral derived tables
- See Aliases for Tables or Views
- See Collection-Derived Table
- See Iterator Functions
- Informix extension
- See Collection Subquery
- Must specify a supertable within a typed table hierarchy
- See The ONLY Keyword
| Element |
Description |
Restrictions |
Syntax |
|---|
| alias |
Temporary name for a table, view, or derived table
in this query |
See Aliases for Tables or Views. |
Identifier |
| derived _column |
Temporary name for a derived column in a table
expression |
Unless the underlying collection is a ROW type, you can declare no more than one
derived_column name |
Identifier |
| external |
External table from which to retrieve data |
Must exist, but cannot be the outer table in an
outer join |
Database Object Name |
| subquery |
Nested query whose results are available to the outer query |
See Table expressions |
SELECT statement |
| synonym, table, view |
Synonym for a table from which to retrieve data |
Synonym and table or view to which it points must exist. Must include appropriate
qualifiers. |
Database Object Name |
Every SELECT statement requires the FROM clause, whether
or not any data source is required. If your query uses the database
server to evaluate an expression that requires no data source, the
FROM clause can reference any existing table in the current database
on which you hold sufficient access privileges, as in the following
example:
SELECT ATANH(SQRT(POW(4,2) + POW(5,2))) FROM systables;