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<title>LuaSQL: Database connectivity for the Lua programming language</title>
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<div id="product_logo"><a href="http://www.keplerproject.org">
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<div id="product_name"><big><b>LuaSQL</b></big></div>
<div id="product_description">Database connectivity for the Lua programming language</div>
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<h1>LuaSQL</h1>
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<li><a href="index.html">Home</a>
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<li><a href="manual.html">Manual</a>
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<li><strong>Examples</strong></li>
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<h2><a name="examples"></a>Examples</h2>
<p>Here is an example of the basic use of the library.
After that, another example shows how to create an
<a href="#iterator_example">iterator</a> over the result of a SELECT
query.</p>
<h3><a name="basic_use"></a>Basic use</h3>
<pre class="example">
-- load driver
local driver = require "luasql.postgres"
-- create environment object
env = assert (driver.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() -- already closed because all the result set was consumed
con:close()
env:close()
</pre>
<p>And the output of this script should be:</p>
<pre class="example">
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
</pre>
<h3><a name="iterator_example"></a>Iterator</h3>
<p>It may be useful to offer an iterator for the resulting rows:</p>
<pre class="example">
function rows (connection, sql_statement)
local cursor = assert (connection:execute (sql_statement))
return function ()
return cursor:fetch()
end
end
</pre>
<p>Here is how the iterator is used:</p>
<pre class="example">
env = assert (require"luasql.mysql".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
</pre>
<p>Obviously, the code above only works if there is a table called contacts with the columns id, name and address in this order. At the end of the loop the cursor will be automatically closed by the driver.</p>
<h3><a name="To_be_closed"></a>To-be-closed Objects</h3>
<p>
<strong style="color: red;">Compatibility Note:</strong>
To-be-closed variables is a feature introduced in Lua 5.4. Therefore, this functionality can only be used if LuaSQL (version > 2.6) is compiled against Lua version 5.4 or higher.
</p>
<pre class="example">
function getName(db, id)
-- This code requires Lua 5.4 or higher due to the use of to-be-closed variables.
local cur <close> = db:execute("SELECT name FROM contacts WHERE id = " .. id)
return cur:fetch()
end
</pre>
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