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pg_execute submits a command to the
PostgreSQL server.
If the command is not a SELECT statement, the number of rows affected by the command is returned. If the command is an INSERT statement and a single row is inserted, the OID of the inserted row is stored in the variable oidVar if the optional -oid argument is supplied.
If the command is a SELECT statement, then, for each row in the result, the row values are stored in the arrayVar variable, if supplied, using the column names as the array indices, else in variables named by the column names, and then the optional procedure is executed if supplied. (Omitting the procedure probably makes sense only if the query will return a single row.) The number of rows selected is returned.
The procedure can use the Tcl commands
break, continue, and
return with the expected behavior. Note that if
the procedure executes
return, then pg_execute
does not return the number of affected rows.
pg_execute is a newer function which provides
a superset of the features of pg_select and
can replace pg_exec in many cases where access
to the result handle is not needed.
For server-handled errors, pg_execute will
throw a Tcl error and return a two-element list. The first element
is an error code, such as PGRES_FATAL_ERROR, and
the second element is the server error text. For more serious
errors, such as failure to communicate with the server,
pg_execute will throw a Tcl error and return
just the error message text.
Specifies the name of an array variable where result rows are stored, indexed by the column names. This is ignored if commandString is not a SELECT statement.
Specifies the name of a variable into which the OID from an INSERT statement will be stored.
The handle of the connection on which to execute the command.
The SQL command to execute.
Optional procedure to execute for each result row of a SELECT statement.
In the following examples, error checking with catch has been omitted for clarity.
Insert a row and save the OID in result_oid:
pg_execute -oid result_oid $pgconn "INSERT INTO mytable VALUES (1);"
Print the columns item and value from each row:
pg_execute -array d $pgconn "SELECT item, value FROM mytable;" {
puts "Item=$d(item) Value=$d(value)"
}
Find the maximum and minimum values and store them in $s(max) and $s(min):
pg_execute -array s $pgconn "SELECT max(value) AS max, min(value) AS min FROM mytable;"
Find the maximum and minimum values and store them in $max and $min:
pg_execute $pgconn "SELECT max(value) AS max, min(value) AS min FROM mytable;"