How to create a table in oracle

Creating an Oracle table involves the following steps: Use the CREATE TABLE syntax to specify table names, column names, data types, constraints, and default values. The table name should be concise and descriptive, and should not exceed 30 characters. The column name should be descriptive, and the data type specifies the data type stored in the column. The NOT NULL constraint ensures that null values ​​are not allowed in the column, and the DEFAULT clause specifies the default values ​​for the column. PRIMARY KEY Constraints to identify the unique record of the table. FOREIGN KEY constraint specifies that the column in the table refers to the primary key in another table. See the creation of the sample table students, which contains primary keys, unique constraints, and default values.

How to create a table in Oracle

Creating tables in Oracle is a basic and important operation to store and manage data. Creating a table involves the following steps:

1. Create table syntax

 <code class="oracle">CREATE TABLE table_name ( column_name data_type [NOT NULL] [DEFAULT default_value], ... );</code>

2. Table name

Table names should be concise and descriptive, and must not exceed 30 characters. Table names should start with letters and contain only letters, numbers, and underscores.

3. Column name and data type

Column names should be descriptive and follow the same naming convention as table names. Data Type Specifies the data type stored in the column. Common types include:

• Number (NUMBER)
• String (VARCHAR2)
• Date (DATE)
• Time (TIMESTAMP)

4. Nullability and default values

NOT NULL constraints ensure that null values ​​are not allowed in the column. The DEFAULT clause specifies the default value of a column and is used when inserting.

5. Primary key constraints

The primary key constraint identifies the unique record of the table. Use PRIMARY KEY constraint to specify one or more columns as primary keys:

 <code class="oracle">PRIMARY KEY (column_name, ...);</code>

6. Foreign key constraints

Foreign key constraints specify that the columns in the specified table refer to the primary key in another table. This ensures data integrity between tables:

 <code class="oracle">FOREIGN KEY (column_name) REFERENCES other_table(primary_key_column);</code>

7. Example

Create a table called students with the following columns:

 <code class="oracle">CREATE TABLE students ( id NUMBER PRIMARY KEY, name VARCHAR2(50) NOT NULL, age NUMBER, email VARCHAR2(100) UNIQUE, gpa NUMBER(3,2) DEFAULT 0.00 );</code>

Note that the id column is the primary key, the email column is the unique constraint, and gpa column has a default value.

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