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authorAndrey Andreev <narf@devilix.net>2015-01-12 16:23:26 +0100
committerAndrey Andreev <narf@devilix.net>2015-01-12 16:23:26 +0100
commit45a8afaabc6d09ad59bbb3c89a6cdfe8cbc3312c (patch)
tree7ca4207099f9225b5ef74b31f48627a282e7fdf2 /user_guide_src/source/database/metadata.rst
parentcd94dd7e1d8969658810ccc4158a75d2936d0a44 (diff)
parent934d6d9797f4dadd4e4d05b12bc4d7309fedb6c3 (diff)
Merge branch 'develop' into feature/session
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+#################
+Database Metadata
+#################
+
+**************
+Table MetaData
+**************
+
+These functions let you fetch table information.
+
+List the Tables in Your Database
+================================
+
+**$this->db->list_tables();**
+
+Returns an array containing the names of all the tables in the database
+you are currently connected to. Example::
+
+ $tables = $this->db->list_tables();
+
+ foreach ($tables as $table)
+ {
+ echo $table;
+ }
+
+
+Determine If a Table Exists
+===========================
+
+**$this->db->table_exists();**
+
+Sometimes it's helpful to know whether a particular table exists before
+running an operation on it. Returns a boolean TRUE/FALSE. Usage example::
+
+ if ($this->db->table_exists('table_name'))
+ {
+ // some code...
+ }
+
+.. note:: Replace *table_name* with the name of the table you are looking for.
+
+
+**************
+Field MetaData
+**************
+
+List the Fields in a Table
+==========================
+
+**$this->db->list_fields()**
+
+Returns an array containing the field names. This query can be called
+two ways:
+
+1. You can supply the table name and call it from the $this->db->
+object::
+
+ $fields = $this->db->list_fields('table_name');
+
+ foreach ($fields as $field)
+ {
+ echo $field;
+ }
+
+2. You can gather the field names associated with any query you run by
+calling the function from your query result object::
+
+ $query = $this->db->query('SELECT * FROM some_table');
+
+ foreach ($query->list_fields() as $field)
+ {
+ echo $field;
+ }
+
+
+Determine If a Field is Present in a Table
+==========================================
+
+**$this->db->field_exists()**
+
+Sometimes it's helpful to know whether a particular field exists before
+performing an action. Returns a boolean TRUE/FALSE. Usage example::
+
+ if ($this->db->field_exists('field_name', 'table_name'))
+ {
+ // some code...
+ }
+
+.. note:: Replace *field_name* with the name of the column you are looking
+ for, and replace *table_name* with the name of the table you are
+ looking for.
+
+
+Retrieve Field Metadata
+=======================
+
+**$this->db->field_data()**
+
+Returns an array of objects containing field information.
+
+Sometimes it's helpful to gather the field names or other metadata, like
+the column type, max length, etc.
+
+.. note:: Not all databases provide meta-data.
+
+Usage example::
+
+ $fields = $this->db->field_data('table_name');
+
+ foreach ($fields as $field)
+ {
+ echo $field->name;
+ echo $field->type;
+ echo $field->max_length;
+ echo $field->primary_key;
+ }
+
+If you have run a query already you can use the result object instead of
+supplying the table name::
+
+ $query = $this->db->query("YOUR QUERY");
+ $fields = $query->field_data();
+
+The following data is available from this function if supported by your
+database:
+
+- name - column name
+- max_length - maximum length of the column
+- primary_key - 1 if the column is a primary key
+- type - the type of the column