Your code must load the sql package using the normal method: package require sql .
Alternatively you can simply load the shared object using something like: load ./sql.so

The sql package adds only a single command to tcl: sql . This command takes several subcommands, as listed below. The subcommands are always the first argument to the sql command. The second argument, if necessary, is the handle for a given connection.

Normal usage would be to create a connection via connect, select a database via selectdb, query or execute sql commands via query and exec, and close the connection using disconnect .

connect <host> <userid> <password>

Connect to the database. Returns the handle from that connection.
Takes two optional arguments, the userid and password.
set conn [sql connect]
set conn2 [sql connect host someuser somepassword]

disconnect handle

Disconnect the given connection.
sql disconnect $conn

selectdb handle dbname

Select the dbname database to be used on the given handle. After doing a connect you must selectdb.
sql selectdb $conn mydatabase

exec handle statement

Execute a sql statement.
sql exec $conn "create table sample (x integer)"

query handle statement

Query the database for some results (generally a select statement). Use with fetchrow and endquery.
sql query $conn "select * from sample where x > 3"

fetchrow handle

Fetch the next row of results. Must be executed after a query statement. The row is returned as a tcl list. If there are no more rows available an empty string is returned.
while {[set row [sql fetchrow $conn]] != ""} { puts $row }

# Load the sql package:
package require sql

# Connect to the database
set conn [sql connect]

# select the database 'test' to be used.
sql selectdb $conn test

# Create a table and put some data in it:
sql exec $conn "create table junk (i integer, r real, s char(10))"

# Put some dummy data in:
for {set i 0} {$i < 10} {incr i} {
	sql exec $conn "insert into junk values ($i, $i.01, 'xx $i xx')"
}

# Do a select and display the results
sql query $conn "select * from junk where i > 3" 

while {[set row [sql fetchrow $conn]] != ""} {
	puts "row = $row"
}

sql endquery $conn

sql exec $conn "drop table junk"
sql disconnect $conn

row = 4 4.0100 {xx 4 xx}
row = 5 5.0100 {xx 5 xx}
row = 6 6.0100 {xx 6 xx}
row = 7 7.0100 {xx 7 xx}
row = 8 8.0100 {xx 8 xx}
row = 9 9.0100 {xx 9 xx}