The
SQL From clause is the source of a rowset to be operated upon in a
Data Manipulation Language (DML) statement. From clauses are very common, and will provide the rowset to be exposed through a
Select statement, the source of values in an
Update statement, and the target rows to be deleted in a
Delete statement.
FROM
is an
SQL reserved word in the
SQL standard.
The
FROM
clause is used in conjunction with SQL statements, and takes the following general form:
''SQL-DML-Statement''
FROM ''table_name''
WHERE ''predicate''
The From clause can generally be anything that returns a rowset, a table, view, function, or system-provided information like the
Information Schema, which is typically running proprietary commands and returning the information in a table form.
Examples
The following query returns only those rows from table ''mytable'' where the value in column ''mycol'' is greater than 100.
SELECT *
FROM mytable
WHERE mycol > 100
Requirement
The From clause is technically required in relational algebra and in most scenarios to be useful. However many relational DBMS implementations may not require it for selecting a single value, or single row - known as
DUAL table The DUAL table is a special one-row, one-column table present by default in Oracle and other database installations. In Oracle, the table has a single VARCHAR2(1) column called DUMMY that has a value of 'X'. It is suitable for use in selecting a pse ...
in
Oracle database
Oracle Database (commonly referred to as Oracle DBMS, Oracle Autonomous Database, or simply as Oracle) is a multi-model database management system produced and marketed by Oracle Corporation.
It is a database commonly used for running online t ...
.
SELECT 3.14 AS Pi
Other systems will require a From statement with a keyword, even to select system data.
select to_char(sysdate, 'Dy DD-Mon-YYYY HH24:MI:SS') as "Current Time"
from dual;
References
{{DEFAULTSORT:From (Sql)
SQL keywords
Articles with example SQL code