This Oracle tutorial explains how to create, drop, disable, and enable a primary key in Oracle with syntax and examples.
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What is a primary key 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.
Note
Create Primary Key - Using CREATE TABLE statement
You can create a primary key in Oracle with the CREATE TABLE statement.
Syntax
The syntax to create a primary key using the CREATE TABLE statement in Oracle/PLSQL is:
![]() Example
Let's look at an example of how to create a primary key using the CREATE TABLE statement in Oracle:
In this example, we've created a primary key on the supplier table called supplier_pk. It consists of only one field - the supplier_id field.
We could also create a primary key with more than one field as in the example below:
Create Primary Key - Using ALTER TABLE statement
You can create a primary key in Oracle with the ALTER TABLE statement.
Syntax
The syntax to create a primary key using the ALTER TABLE statement in Oracle/PLSQL is:
Example
Let's look at an example of how to create a primary key using the ALTER TABLE statement in Oracle.
In this example, we've created a primary key on the existing supplier table called supplier_pk. It consists of the field called supplier_id.
We could also create a primary key with more than one field as in the example below:
Drop Primary Key
You can drop a primary key in Oracle using the ALTER TABLE statement.
Syntax
The syntax to drop a primary key using the ALTER TABLE statement in Oracle/PLSQL is:
Example
Let's look at an example of how to drop a primary key using the ALTER TABLE statement in Oracle.
In this example, we're dropping a primary key on the supplier table called supplier_pk.
Disable Primary Key
You can disable a primary key in Oracle using the ALTER TABLE statement.
Syntax
The syntax to disable a primary key using the ALTER TABLE statement in Oracle/PLSQL is:
Example
Let's look at an example of how to disable a primary using the ALTER TABLE statement in Oracle.
In this example, we're disabling a primary key on the supplier table called supplier_pk.
Enable Primary Key
You can enable a primary key in Oracle using the ALTER TABLE statement.
Syntax
The syntax to enable a primary key using the ALTER TABLE statement in Oracle/PLSQL is:
Example
Let's look at an example of how to enable a primary key using the ALTER TABLE statement in Oracle.
In this example, we're enabling a primary key on the supplier table called supplier_pk.
The
DBMS_RANDOM package provides a built-in random number generator.
This chapter contains the following topics:
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Note:
DBMS_RANDOM is not intended for cryptography.
Using DBMS_RANDOMOperational notes
DBMS_RANDOM can be explicitly initialized but does not require initialization before a call to the random number generator. It automatically initializes with the date, user ID, and process ID if no explicit initialization is performed.
If this package is seeded twice with the same seed, then accessed in the same way, it produces the same result in both cases.
In some cases, such as when testing, you may want the sequence of random numbers to be the same on every run. In that case, you seed the generator with a constant value by calling an overload of
SEED . To produce different output for every run, simply omit the seed call. Then the system chooses a suitable seed for you.
Summary of DBMS_RANDOM subprograms
Table 6-1 DBMS_RANDOM package subprograms
Note:
The INITIALIZE procedure, RANDOM function and TERMINATE procedure are deprecated. They are included in this release for legacy reasons only.
Notes:
INITIALIZE procedure
This procedure is deprecated. Although currently supported, it should not be used. It initializes the random number generator.
Parameters
Table 6-2 INITIALIZE procedure parameters
Usage notes
This procedure is obsolete as it simply calls the SEED procedure.
NORMAL function
This function returns random numbers in a standard normal distribution. https://pricenew.weebly.com/myeclipse-key-generator-free-download.html.
Return value
The random number, a
NUMBER value
RANDOM function
This procedure is deprecated. Although currently supported, it should not be used. https://pricenew.weebly.com/mpeg-2-license-key-generator-raspberry-pi.html. It generates and returns a random number.
Return value
A random
BINARY_INTEGER value greater than or equal to -power(2,31) and less than power(2,31)
Generate Random Key In Oracle Login
Usage notes
See the NORMAL function and the VALUE function.
SEED procedure
This procedure resets the seed used in generating a random number. https://pricenew.weebly.com/generate-key-for-google-authenticator.html.
Parameters
Table 6-3 SEED procedure parameters
Usage notes
The seed can be a string up to length 2000.
STRING function
This function generates and returns a random string.
Parameters
Table 6-4 STRING function parameters
Return value
A
VARCHAR2 value with the random string
TERMINATE procedure
This procedure is deprecated. Although currently supported, it should not be used. It would be called when the user is finished with the package.
VALUE function
One version returns a random number, greater than or equal to 0 and less than 1, with 38 digits to the right of the decimal (38-digit precision). The other version returns a random Oracle Database
NUMBER value x , where x is greater than or equal to the specified low value and less than the specified high value.
Parameters
Generate Random Key In Oracle Software
Table 6-5 VALUE function parameters
Oracle Generate Random Integer
Return value
Generate Random Key In Oracle Login
A
NUMBER value that is the generated random number
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