'\" t
.\"     Title: dblink_build_sql_update
.\"    Author: The PostgreSQL Global Development Group
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 2021
.\"    Manual: PostgreSQL 9.6.24 Documentation
.\"    Source: PostgreSQL 9.6.24
.\"  Language: English
.\"
.TH "DBLINK_BUILD_SQL_UPDATE" "3" "2021" "PostgreSQL 9.6.24" "PostgreSQL 9.6.24 Documentation"
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.SH "NAME"
dblink_build_sql_update \- builds an UPDATE statement using a local tuple, replacing the primary key field values with alternative supplied values
.SH "SYNOPSIS"
.sp
.nf
dblink_build_sql_update(text relname,
                        int2vector primary_key_attnums,
                        integer num_primary_key_atts,
                        text[] src_pk_att_vals_array,
                        text[] tgt_pk_att_vals_array) returns text
.fi
.SH "DESCRIPTION"
.PP
\fBdblink_build_sql_update\fR
can be useful in doing selective replication of a local table to a remote database\&. It selects a row from the local table based on primary key, and then builds a SQL
\fBUPDATE\fR
command that will duplicate that row, but with the primary key values replaced by the values in the last argument\&. (To make an exact copy of the row, just specify the same values for the last two arguments\&.) The
\fBUPDATE\fR
command always assigns all fields of the row \(em the main difference between this and
\fBdblink_build_sql_insert\fR
is that it\*(Aqs assumed that the target row already exists in the remote table\&.
.SH "ARGUMENTS"
.PP
\fIrelname\fR
.RS 4
Name of a local relation, for example
foo
or
myschema\&.mytab\&. Include double quotes if the name is mixed\-case or contains special characters, for example
"FooBar"; without quotes, the string will be folded to lower case\&.
.RE
.PP
\fIprimary_key_attnums\fR
.RS 4
Attribute numbers (1\-based) of the primary key fields, for example
1 2\&.
.RE
.PP
\fInum_primary_key_atts\fR
.RS 4
The number of primary key fields\&.
.RE
.PP
\fIsrc_pk_att_vals_array\fR
.RS 4
Values of the primary key fields to be used to look up the local tuple\&. Each field is represented in text form\&. An error is thrown if there is no local row with these primary key values\&.
.RE
.PP
\fItgt_pk_att_vals_array\fR
.RS 4
Values of the primary key fields to be placed in the resulting
\fBUPDATE\fR
command\&. Each field is represented in text form\&.
.RE
.SH "RETURN VALUE"
.PP
Returns the requested SQL statement as text\&.
.SH "NOTES"
.PP
As of
PostgreSQL
9\&.0, the attribute numbers in
\fIprimary_key_attnums\fR
are interpreted as logical column numbers, corresponding to the column\*(Aqs position in
SELECT * FROM relname\&. Previous versions interpreted the numbers as physical column positions\&. There is a difference if any column(s) to the left of the indicated column have been dropped during the lifetime of the table\&.
.SH "EXAMPLES"
.sp
.if n \{\
.RS 4
.\}
.nf
SELECT dblink_build_sql_update(\*(Aqfoo\*(Aq, \*(Aq1 2\*(Aq, 2, \*(Aq{"1", "a"}\*(Aq, \*(Aq{"1", "b"}\*(Aq);
                   dblink_build_sql_update
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
 UPDATE foo SET f1=\*(Aq1\*(Aq,f2=\*(Aqb\*(Aq,f3=\*(Aq1\*(Aq WHERE f1=\*(Aq1\*(Aq AND f2=\*(Aqb\*(Aq
(1 row)
.fi
.if n \{\
.RE
.\}