Αποτελέσματα Αναζήτησης
This tutorial shows you how to use Oracle PRIMARY KEY constraint to create, add, disable, enable, and drop a primary key of a table.
To create a PRIMARY KEY constraint on the "ID" column when the table is already created, use the following SQL: MySQL / SQL Server / Oracle / MS Access: ALTER TABLE Persons. ADD PRIMARY KEY (ID);
To create a new table with a column defined as the primary key, you can use the keyword PRIMARY KEY at the end of the definition of that column. In our example, we create the table product using a CREATE TABLE clause, with the names of the columns and their respective data types in parentheses.
The syntax to create a primary key using the CREATE TABLE statement in Oracle/PLSQL is: CREATE TABLE table_name. ( column1 datatype null/not null, column2 datatype null/not null, ... CONSTRAINT constraint_name PRIMARY KEY (column1, column2, ... column_n) ); Example.
The PRIMARY KEY constraint in SQL is a combination of NOT NULL and UNIQUE constraints and is used to uniquely identify the row. In this tutorial, you will learn about the PRIMARY KEY constraint in SQL with the help of examples.
CREATE TABLE table_name( column1 datatype, column2 datatype, . ..., PRIMARY KEY(column1) ); In this syntax, you define the PRIMARY KEY constraint as a table constraint. Defining a multi-column primary key. If the primary key consists of two or more columns, you need to use a table constraint to define the primary key: CREATE TABLE table_name(
The syntax to create a primary key using the CREATE TABLE statement in SQL is: CREATE TABLE table_name. ( column1 datatype [ NULL | NOT NULL ], column2 datatype [ NULL | NOT NULL ], ... CONSTRAINT constraint_name PRIMARY KEY (pk_col1, pk_col2, ... pk_col_n) ); OR. CREATE TABLE table_name. ( column1 datatype CONSTRAINT constraint_name PRIMARY KEY,
