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><H1
><A
NAME="PG-SELECT"
></A
>pg_select</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN1048"
></A
><H2
>Name</H2
>pg_select -- loop over the result of a query</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN1051"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>pg_select <VAR
CLASS="PARAMETER"
>conn</VAR
> <VAR
CLASS="PARAMETER"
>commandString</VAR
> <VAR
CLASS="PARAMETER"
>arrayVar</VAR
> <VAR
CLASS="PARAMETER"
>procedure</VAR
></PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1057"
></A
><H2
>Description</H2
><P
><CODE
CLASS="FUNCTION"
>pg_select</CODE
> submits a query (<TT
CLASS="COMMAND"
>SELECT</TT
>
statement) to the <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> server and executes
a given chunk of code for each row in the result. The
<VAR
CLASS="REPLACEABLE"
>commandString</VAR
> must be a <TT
CLASS="COMMAND"
>SELECT</TT
>
statement; anything else returns an error. The
<VAR
CLASS="REPLACEABLE"
>arrayVar</VAR
> variable is an array name used in the loop.
For each row, <VAR
CLASS="REPLACEABLE"
>arrayVar</VAR
> is filled in with the row
values, using the column names as the array indices. Then the
<VAR
CLASS="REPLACEABLE"
>procedure</VAR
> is executed.
</P
><P
> In addition to the column values, the following special entries are
made in the array:
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>.headers</TT
></DT
><DD
><P
> A list of the column names returned by the query.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>.numcols</TT
></DT
><DD
><P
> The number of columns returned by the query.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>.tupno</TT
></DT
><DD
><P
> The current row number, starting at zero and incrementing for
each iteration of the loop body.
</P
></DD
></DL
></DIV
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1085"
></A
><H2
>Arguments</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><VAR
CLASS="REPLACEABLE"
>conn</VAR
></DT
><DD
><P
> The handle of the connection on which to execute the query.
</P
></DD
><DT
><VAR
CLASS="REPLACEABLE"
>commandString</VAR
></DT
><DD
><P
> The SQL query to execute.
</P
></DD
><DT
><VAR
CLASS="REPLACEABLE"
>arrayVar</VAR
></DT
><DD
><P
> An array variable for returned rows.
</P
></DD
><DT
><VAR
CLASS="REPLACEABLE"
>procedure</VAR
></DT
><DD
><P
> The procedure or script to run for each returned row.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1108"
></A
><H2
>Return Value</H2
><P
> None
</P
><P
> A Tcl error will be thrown if an error occurs communicating with
the database, or if there is an error processing the query, or
if the procedure body throws a Tcl error.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1112"
></A
><H2
>Notes</H2
><P
> <A
HREF="pg-execute.html"
>pg_execute</A
> is a newer command which provides more
features and is more flexible than <CODE
CLASS="FUNCTION"
>pg_select</CODE
>.
</P
><P
> This command uses or emulates the <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>
<SPAN
CLASS="APPLICATION"
>libpq</SPAN
>
function <CODE
CLASS="FUNCTION"
>PQexec</CODE
>.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1121"
></A
><H2
>Examples</H2
><P
> This examples assumes that the table <CODE
CLASS="CLASSNAME"
>table1</CODE
> has
columns <TT
CLASS="STRUCTFIELD"
>control</TT
> and
<TT
CLASS="STRUCTFIELD"
>name</TT
> (and perhaps others):
</P><PRE
CLASS="PROGRAMLISTING"
>pg_select $conn "SELECT * FROM table1" array {
puts [format "%5d %s" $array(control) $array(name)]
}</PRE
><P>
</P
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