![]() ![]() CREATE TABLE countries (īecause the primary key of the countries table has only one column, we defined the primary key using PRIMARY KEY column constraint. The following statement creates a table named countries which has country_id column as the primary key. ) Code language: SQL (Structured Query Language) ( sql ) Creating SQLite primary key examples It is faster than using a primary key which is not an alias of the rowid.Īnother important note is that if you declare a column with the INTEGER type and PRIMARY KEY DESC clause, this column will not become an alias for the rowid column: CREATE TABLE table( Notice that if you assign another integer type such as BIGINT and UNSIGNED INT to the primary key column, this column will not be an alias for the rowid column.īecause the rowid table organizes its data as a B-tree, querying and sorting data of a rowid table are very fast. ![]() If a table has the primary key that consists of one column, and that column is defined as INTEGER then this primary key column becomes an alias for the rowid column. Tables that have rowid columns are called rowid tables. The rowid column is a key that uniquely identifies the rows in the table. When you create a table without specifying the WITHOUT ROWID option, SQLite adds an implicit column called rowid that stores 64-bit signed integer. However, to make the current version of SQLite compatible with the earlier version, SQLite allows the primary key column to contain NULL values. It means that the primary key column has an implicit NOT NULL constraint. In SQL standard, the primary key column must not contain NULL values. ) Code language: SQL (Structured Query Language) ( sql ) ![]() Second, in case primary key consists of two or more columns, you use the PRIMARY KEY table constraint to define the primary as shown in the following statement. SQLite allows you to define primary key in two ways:įirst, if the primary key has only one column, you use the PRIMARY KEY column constraint to define the primary key as follows: CREATE TABLE table_name( Each table has one and only one primary key. Introduction to SQLite primary keyĪ primary key is a column or group of columns used to identify the uniqueness of rows in a table. This example we've created a primary key called contacts_pk that is made up of a combination of the last_name and first_name columns.Summary: in this tutorial, you will learn how to use SQLite PRIMARY KEY constraint to define a primary key for a table. We could also create a primary key with more than one field as in the example below: ALTER TABLE order_details It consists of the order_detail_id column. In this example, we've created a primary key on the existing order_details table called order_details_pk. Let's look at an example of how to create a primary key using the ALTER TABLE statement in PostgreSQL. index_col_n The columns that make up the primary key. constraint_name The name of the primary key. index_col_n) table_name The name of the table to modify. The syntax to create a primary key using the ALTER TABLE statement in PostgreSQL is: ALTER TABLE table_name You can create a primary key in PostgreSQL with the ALTER TABLE statement. So each combination of order_date and customer_id must be unique in the order_details table.Ĭreate Primary Key - Using ALTER TABLE statement This example creates a primary key called order_details_pk that is made up of a combination of the order_date and customer_id columns. We could also create a primary key with more than one field as in the example below: CREATE TABLE order_detailsĬONSTRAINT order_details_pk PRIMARY KEY (order_date, customer_id) ![]() It consists of only one column - the order_detail_id column. In these two examples, we've created a primary key on the order_details table called order_details_pk. ( order_detail_id integer CONSTRAINT order_details_pk PRIMARY KEY, Or you could also create the primary key on the order_details table using the following syntax: CREATE TABLE order_details CREATE TABLE order_detailsĬONSTRAINT order_details_pk PRIMARY KEY (order_detail_id) Let's look at an example of how to create a primary key using the CREATE TABLE statement in PostgreSQL. See the PostgreSQL CREATE TABLE statement for more detailed CREATE TABLE syntax as this is an over-simplification to demonstrate how to create a Primary Key. column1, column2 The columns that you wish to create in the table. ) table_name The name of the table that you wish to create. index_col_n)Ĭolumn1 datatype CONSTRAINT constraint_name PRIMARY KEY, The syntax to create a primary key using the CREATE TABLE statement in PostgreSQL is: CREATE TABLE table_name You can create a primary key in PostgreSQL with the CREATE TABLE statement. Create Primary Key - Using CREATE TABLE statement ![]()
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