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<div id="product_name"><big><b>LuaSQL</b></big></div>
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<h1>LuaSQL</h1>
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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
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()
</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 use</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">
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
</pre>
<p>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).</p>
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