CODEWITHSUNDEEP
mysqlprimary-keykey
user167850
user167850

Reputation: 497

Primary key versus key

When creating a mysql dump containing the structure of my database, one of the tables shows the following:

CREATE TABLE `completedTransactions` (
  `paymentId` int(10) unsigned NOT NULL,
  `timestamp` int(15) unsigned NOT NULL,
  `actionTaken` varchar(25) NOT NULL,
  `response` varchar(255) NOT NULL,
  `responseCode` int(5) NOT NULL,

  PRIMARY KEY  (`paymentId`,`timestamp`),
  KEY `paymentId` (`paymentId`),

The primary key is what I was expecting, but I'm unsure what the last line is about?

KEY `paymentId` (`paymentId`),

Is this related to an index?

Upvotes: 13

Views: 7786

Answers (3)

Notinlist
Notinlist

Reputation: 16640

KEY is not unique, PRIMARY KEY and UNIQUE KEY are uniques.

Upvotes: 3

Pascal MARTIN
Pascal MARTIN

Reputation: 400932

Quoting the documentation of CREATE TABLE :

KEY is normally a synonym for INDEX.
The key attribute PRIMARY KEY can also be specified as just KEY when given in a column definition. This was implemented for compatibility with other database systems.

Upvotes: 2

Daniel Vassallo
Daniel Vassallo

Reputation: 344281

Yes, the KEY keyword is just an alias for the INDEX keyword.

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
  ...
  {INDEX|KEY} [index_name] [index_type] (index_col_name,...)
      [index_option] ...

Source: MySQL Documentation: CREATE TABLE

Upvotes: 13

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