What is primary key constraint in Oracle?

What is primary key constraint in Oracle?

In Oracle, a primary key is a single field or combination of fields that uniquely defines a record. None of the fields that are part of the primary key can contain a null value. A table can have only one primary key.

How can I make Sqlldr faster?

These include:

1. Use Direct Path Loads – The conventional path loader essentially loads the data by using standard insert statements.
2. Disable Indexes and Constraints.
3. Use a Larger Bind Array.
4. Use ROWS=n .
5. Use Parallel Loads.
6. Use Fixed Width Data.
7. Disable Archiving During Load.
8. Use unrecoverable.

What are the constraints in Oracle explain primary key constraints with examples?

The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields).

What is a primary key constraint?

The PRIMARY KEY constraint specifies that the constrained columns’ values must uniquely identify each row. A table’s primary key should be explicitly defined in the CREATE TABLE statement. Tables can only have one primary key.

Why SQL * Loader is faster than insert?

3 Answers. SQL*Loader is the more efficient method. It gives you more control. You have an option do DIRECT load and NOLOGGING , which will reduce redo log generation, and when indexes have been disabled (as part of direct loading), the loading goes faster.

What are primary key constraints?

What is Pragma INIT exception in Oracle?

The pragma EXCEPTION_INIT associates an exception name with an Oracle error number. You can intercept any ORA- error and write a specific handler for it instead of using the OTHERS handler. A user-defined exception declared within the current scope. PRAGMA. Signifies that the statement is a compiler directive.

What are the two rules of primary key?

The general rules when designing a primary key are:

• The primary key value must uniquely identify one and only one record within the table.
• The primary key value must NOT be null.
• The primary key value must NOT change.

What is primary key in Oracle?

Primary key is a type of constraint used in Oracle tables.A primary key is used to uniquely identify each row in a table.A primary key can consist of one or more fields on a table.

How to drop constraints in Oracle?

We can drop constraint in Oracle database by using constraint-name. The constraint name can be generated by Oracle database or user-defined name. But there is a separate story for NOT NULL constraint and PRIMARY KEY constraint.

How to add primary key constraints?

In Object Explorer,right-click the table to which you want to add a unique constraint,and click Design.

In Table Designer,click the row selector for the database column you want to define as the primary key.

Right-click the row selector for the column and select Set Primary Key.

How to define check constraint in Oracle?

Introduction to Oracle Check constraint. An Oracle check constraint allows you to enforce domain integrity by limiting the values accepted by one or more columns.

Creating Check constraint syntax.

Add Check constraint to a table.

Drop checking constraint

Disable/Enable check constraint

Restrictions of Oracle check constraint.