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134 lines
3.2 KiB
Plaintext
134 lines
3.2 KiB
Plaintext
.\" This is -*-nroff-*-
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.\" XXX standard disclaimer belongs here....
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.\" $Header: /cvsroot/pgsql/doc/man/Attic/select.l,v 1.2 1996/10/07 02:34:53 momjian Exp $
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.TH SELECT SQL 11/05/95 Postgres95 Postgres95
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.SH NAME
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select \(em retrieve instances from a class
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.SH SYNOPSIS
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.nf
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\fBselect\fR [distinct]
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expression1 [\fBas\fR attr_name-1]
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{, expression-1 [\fBas\fR attr_name-i]}
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[\fBinto\fR \fBtable\fR classname]
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[\fBfrom\fR from-list]
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[\fBwhere\fR where-clause]
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[\fBgroup by\fR attr_name1 {, attr_name-i....}
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[\fBorder by\fR attr_name1
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[\fBusing op1\fR] {, attr_namei [\fBusing opi\fR] }
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.fi
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.SH DESCRIPTION
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.BR Select
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will get all instances which satisfy the qualification,
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.IR qual ,
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compute the value of each element in the target list, and either (1)
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return them to an application program through one of two different
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kinds of portals or (2) store them in a new class.
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.PP
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If
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into table class name
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is specified, the result of the query will be stored in a new class
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with the indicated name.
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.PP
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The
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.BR "order by"
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clause allows a user to specify that he wishes the instances sorted
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according to the corresponding operator. This operator must be a
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binary one returning a boolean. Multiple sort fields are allowed and
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are applied from left to right.
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.PP
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The target list specifies the fields to be retrieved. Each
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.IR attr_name
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specifies the desired attribute or portion of an array attribute.
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Thus, each
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.IR attr_name
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takes the form
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.nf
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class_name.att_name
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.fi
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or, if the user only desires part of an array,
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.nf
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--
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--Specify a lower and upper index for each dimension
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--(i.e., clip a range of array elements)
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--
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class_name.att_name[lIndex-1:uIndex-1]..[lIndex-i:uIndex-i]
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--
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--Specify an exact array element
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--
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class_name.att_name[uIndex-1]..[uIndex-i]
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.fi
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where each
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.IR lIndex
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or
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.IR uIndex
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is an integer constant.
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.PP
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When you retrieve an attribute which is of a complex type, the behavior
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of the system depends on whether you used "nested dots" to project
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out attributes of the complex type or not. See the examples below.
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.PP
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You must have read access to a class to read its values (see
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.IR "grant/revoke" (l).
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.SH EXAMPLES
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.nf
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--
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--Find all employees who make more than their manager
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--
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select e.name
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from emp e, emp m
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where e.mgr = m.name
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and e.sal > m.sal
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.fi
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.nf
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--
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--Retrieve all fields for those employees who make
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--more than the average salary
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--
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select avg(sal) as ave
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into table avgsal from emp;
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.fi
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.nf
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--
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--Retrieve all employee names in sorted order
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--
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select distinct name
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from emp
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order by name using <
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.fi
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.nf
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--
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--Retrieve all employee names that were valid on 1/7/85
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--in sorted order
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--
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selec name
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from emp['January 7 1985'] e
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order by name using <
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.fi
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.nf
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--
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--Construct a new class, raise, containing 1.1
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--times all employee's salaries
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--
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select 1.1 * emp.salary as salary
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into tables raise
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from emp
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.fi
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.SH "SEE ALSO"
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insert(l),
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close(l),
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create table(l),
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fetch(l),
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update(l).
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.SH BUGS
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.BR "Select into"
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does not delete duplicates.
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.PP
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If the backend crashes in the course of executing a
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.BR "select into" ,
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the class file will remain on disk. It can be safely removed by the
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database DBA, but a subsequent
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.BR "select into"
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to the same name will fail with a cryptic error message about
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\*(lqBlockExtend\*(rq.
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