Examples
Below is a small sample code displaying the basic use of the library. After that, another example shows how to create an iterator over the result of a select query.
Basic use
-- load driver
require"luasql.postgres"
-- create environment object
env = assert (luasql.postgres())
-- connect to data source
con = assert (env:connect("luasql-test"))
-- reset our table
res = con:execute"DROP TABLE people"
res = assert (con:execute[[
CREATE TABLE people(
name varchar(50),
email varchar(50)
)
]])
-- add a few elements
list = {
{ name="Jose das Couves", email="jose@couves.com", },
{ name="Manoel Joaquim", email="manoel.joaquim@cafundo.com", },
{ name="Maria das Dores", email="maria@dores.com", },
}
for i, p in pairs (list) do
res = assert (con:execute(string.format([[
INSERT INTO people
VALUES ('%s', '%s')]], p.name, p.email)
))
end
-- retrieve a cursor
cur = assert (con:execute"SELECT name, email from people")
-- print all rows, the rows will be indexed by field names
row = cur:fetch ({}, "a")
while row do
print(string.format("Name: %s, E-mail: %s", row.name, row.email))
-- reusing the table of results
row = cur:fetch (row, "a")
end
-- close everything
cur:close()
con:close()
env:close()
And the output of this script should be:
Name: Jose das Couves, E-mail: jose@couves.com Name: Manoel Joaquim, E-mail: manoel.joaquim@cafundo.com Name: Maria das Dores, E-mail: maria@dores.com
Iterator use
It may be useful to offer an iterator for the resulting rows:
function rows (connection, sql_statement)
local cursor = assert (connection:execute (sql_statement))
return function ()
return cursor:fetch()
end
end
This iterator is used like:
require"luasql.mysql"
env = assert (luasql.mysql())
con = assert (env:connect"my_db")
for id, name, address in rows (con, "select * from contacts") do
print (string.format ("%s: %s", name, address))
end
The iterator could be improved to give better error messages (including the SQL statement, for example) and also explicit close the cursor (by checking whether there are no more rows). The above implementation will rely on the garbage collector to close the cursor.