How to get primary key of table?

Question

Is there a way to get the name of primary key field from mysql-database? For example:

I have a table like this:

+----+------+
| id | name |
+----+---         


        

Answer 1

For a PHP approach, you can use mysql_field_flags

$q = mysql_query('select * from table limit 1');

for($i = 0; $i < mysql_num_fields(); $i++)
    if(strpos(mysql_field_tags($q, $i), 'primary_key') !== false)
        echo mysql_field_name($q, $i)." is a primary key\n";

Answer 2

Shortest possible code seems to be something like

// $dblink contain database login details 
// $tblName the current table name 
$r = mysqli_fetch_assoc(mysqli_query($dblink, "SHOW KEYS FROM $tblName WHERE Key_name = 'PRIMARY'")); 
$iColName = $r['Column_name']; 

Answer 3

SELECT k.column_name
FROM information_schema.key_column_usage k   
WHERE k.table_name = 'YOUR TABLE NAME' AND k.constraint_name LIKE 'pk%'

I would recommend you to watch all the fields

Answer 4

use:

show columns from tablename where `Key` = "PRI";

Answer 5

If you want to generate the list of primary keys dynamically via PHP in one go without having to run through each table you can use

SELECT TABLE_NAME, COLUMN_NAME
FROM INFORMATION_SCHEMA.key_column_usage 
WHERE table_schema = '$database_name' AND CONSTRAINT_NAME = 'PRIMARY' 

though you do need to have access to the information.schema to do this.

Answer 6

MySQL has a SQL query "SHOW INDEX FROM" which returns the indexes from a table. For eg. - the following query will show all the indexes for the products table:-

SHOW INDEXES FROM products \G

It returns a table with type, column_name, Key_name, etc. and displays output with all indexes and primary keys as -

*************************** 1. row ***************************
        Table: products
   Non_unique: 0
     Key_name: PRIMARY
 Seq_in_index: 1
  Column_name: product_id
    Collation: A
  Cardinality: 0
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 

To just display primary key from the table use :-

SHOW INDEXES FROM table_name WHERE Key_name = 'PRIMARY'