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authorAndrey Andreev <narf@devilix.net>2017-06-19 10:33:58 +0200
committerAndrey Andreev <narf@devilix.net>2017-06-19 10:33:58 +0200
commit6c7a4266410070d30f8f6bcdf9c9e67f3d6478e3 (patch)
treef0aab8f6f5e781d5947b1a5553b6648eb7b7a4ab /user_guide_src/source/database/metadata.rst
parent2459285b91d6fc4f5099f9f597529cce1059cb33 (diff)
[ci skip] 3.1.5 release
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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