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diff --git a/user_guide_src/source/database/queries.rst b/user_guide_src/source/database/queries.rst new file mode 100644 index 000000000..11dd78392 --- /dev/null +++ b/user_guide_src/source/database/queries.rst @@ -0,0 +1,151 @@ +####### +Queries +####### + +$this->db->query(); +=================== + +To submit a query, use the following function:: + + $this->db->query('YOUR QUERY HERE'); + +The query() function returns a database result **object** when "read" +type queries are run, which you can use to :doc:`show your +results <results>`. When "write" type queries are run it simply +returns TRUE or FALSE depending on success or failure. When retrieving +data you will typically assign the query to your own variable, like +this:: + + $query = $this->db->query('YOUR QUERY HERE'); + +$this->db->simple_query(); +=========================== + +This is a simplified version of the $this->db->query() method. It DOES +NOT return a database result set, nor does it set the query timer, or +compile bind data, or store your query for debugging. It simply lets you +submit a query. Most users will rarely use this function. + +It returns whatever the database drivers' "execute" function returns. +That typically is TRUE/FALSE on success or failure for write type queries +such as INSERT, DELETE or UPDATE statements (which is what it really +should be used for) and a resource/object on success for queries with +fetchable results. + +:: + + if ($this->db->simple_query('YOUR QUERY')) + { + echo "Success!"; + } + else + { + echo "Query failed!"; + } + +.. note:: PostgreSQL's pg_exec() function always returns a resource on + success, even for write type queries. So take that in mind if + you're looking for a boolean value. + +*************************************** +Working with Database prefixes manually +*************************************** + +If you have configured a database prefix and would like to prepend it to +a table name for use in a native SQL query for example, then you can use +the following:: + + $this->db->dbprefix('tablename'); // outputs prefix_tablename + + +If for any reason you would like to change the prefix programatically +without needing to create a new connection, you can use this method:: + + $this->db->set_dbprefix('newprefix'); + $this->db->dbprefix('tablename'); // outputs newprefix_tablename + + +********************** +Protecting identifiers +********************** + +In many databases it is advisable to protect table and field names - for +example with backticks in MySQL. **Query Builder queries are +automatically protected**, however if you need to manually protect an +identifier you can use:: + + $this->db->protect_identifiers('table_name'); + + +This function will also add a table prefix to your table, assuming you +have a prefix specified in your database config file. To enable the +prefixing set TRUE (boolen) via the second parameter:: + + $this->db->protect_identifiers('table_name', TRUE); + + +**************** +Escaping Queries +**************** + +It's a very good security practice to escape your data before submitting +it into your database. CodeIgniter has three methods that help you do +this: + +#. **$this->db->escape()** This function determines the data type so + that it can escape only string data. It also automatically adds + single quotes around the data so you don't have to: + :: + + $sql = "INSERT INTO table (title) VALUES(".$this->db->escape($title).")"; + +#. **$this->db->escape_str()** This function escapes the data passed to + it, regardless of type. Most of the time you'll use the above + function rather than this one. Use the function like this: + :: + + $sql = "INSERT INTO table (title) VALUES('".$this->db->escape_str($title)."')"; + +#. **$this->db->escape_like_str()** This method should be used when + strings are to be used in LIKE conditions so that LIKE wildcards + ('%', '\_') in the string are also properly escaped. + +:: + + $search = '20% raise'; $sql = "SELECT id FROM table WHERE column LIKE '%".$this->db->escape_like_str($search)."%'"; + + +************** +Query Bindings +************** + +Bindings enable you to simplify your query syntax by letting the system +put the queries together for you. Consider the following example:: + + $sql = "SELECT * FROM some_table WHERE id = ? AND status = ? AND author = ?"; + $this->db->query($sql, array(3, 'live', 'Rick')); + +The question marks in the query are automatically replaced with the +values in the array in the second parameter of the query function. + +The secondary benefit of using binds is that the values are +automatically escaped, producing safer queries. You don't have to +remember to manually escape data; the engine does it automatically for +you. + +*************** +Handling Errors +*************** + +$this->db->error(); +=================== + +If you need to get the last error that has occured, the error() method +will return an array containing its code and message. Here's a quick +example:: + + if ( ! $this->db->simple_query('SELECT `example_field` FROM `example_table`')) + { + $error = $this->db->error(); // Has keys 'code' and 'message' + } + |