LuaSQL
Database connectivity for the Lua programming language

Examples

Here is an example of 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

Here is how the iterator is used:

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 above implementation relies on the garbage collector to close the cursor. It could be improved to give better error messages (including the SQL statement) or to explicitly close the cursor (by checking whether there are no more rows).

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$Id: manual.html,v 1.24 2007/08/27 21:46:04 carregal Exp $