pg_select — Execute an SQL command on the server and loop over the results


pg_select conn commandString arrayVar procedure


pg_select submits a query (SELECT statement) to the PostgreSQL server and executes a given chunk of code for each row in the result. The commandString must be a SELECT statement; anything else returns an error. The arrayVar variable is an array name used in the loop. For each row, arrayVar is filled in with the row values, using the column names as the array indices. Then the procedure is executed.

In addition to the column values, the following special entries are made in the array:


A list of the column names returned by the query.


The number of columns returned by the query.


The current row number, starting at zero and incrementing for each iteration of the loop body.



The handle of the connection on which to execute the command.


The SQL query to execute.


An array variable for returned rows.


The procedure or script to run for each returned row.

Return Value


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.


pg_execute is a newer command which provides more features and is more flexible than pg_select.

This command uses or emulates the PostgreSQL libpq function PQexec.


This examples assumes that the table table1 has columns control and name (and perhaps others):

pg_select $conn "SELECT * FROM table1" array {
    puts [format "%5d %s" $array(control) $array(name)]
} Logo

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