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NULLS LAST Function in Oracle SQL – PLSQL

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The NULLS LAST Function in Oracle SQL / PLSQL is used to place the NULL records at the end in the fetched records.

Syntax for using the NULLS LAST function in Oracle SQL / PLSQL is ;
SELECT column(s)
ROW_NUMBER() OVER (ORDER BY column NULLS LAST)
FROM table_name;

Suppose we have a table named ‘employee’ as shown below:

Employee_ID Employee_Name Salary Department Commission
101 Emp A 10000 Sales 10
102 Emp B 20000 IT 20
103 Emp C 28000 IT 20
104 Emp D 30000 Support
105 Emp E 32000 Sales 10
106 Emp F 40000 Sales 10
107 Emp G 12000 Sales 10
108 Emp H 12000 Sales

Now, suppose we want to see the employee_name and commission and also want that the employee records having no commission should be listed LAST then we can achieve the same using NULLS LAST function as:

SELECT employee_name
       ,commission
       ,ROW_NUMBER () OVER (ORDER BY commission NULLS LAST) SNO
FROM employee;

We will get the following result:

Employee_Name Commission SNO
Emp G 10 1
Emp A 10 2
Emp E 10 3
Emp F 10 4
Emp B 20 5
Emp C 20 6
Emp H   7
Emp D   8

Here we can see that we have successfully fetched employees having no commission LAST in the list.

NULLS FIRST Function in Oracle SQL – PLSQL

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The NULLS FIRST Function in Oracle SQL / PLSQL is used to place the NULL records at the beginning in the fetched records.

Syntax for using the NULLS FIRST function in Oracle SQL / PLSQL is ;
SELECT column(s)
ROW_NUMBER() OVER (ORDER BY column NULLS FIRST)
FROM table_name;

Suppose we have a table named ‘employee’ as shown below:

Employee_ID Employee_Name Salary Department Commission
101 Emp A 10000 Sales 10
102 Emp B 20000 IT 20
103 Emp C 28000 IT 20
104 Emp D 30000 Support
105 Emp E 32000 Sales 10
106 Emp F 40000 Sales 10
107 Emp G 12000 Sales 10
108 Emp H 12000 Sales

Now, suppose we want to see the employee_name and commission and also want that the employees having no commission should be listed first then we can achieve the same using NULLS FIRST function as:

SELECT employee_name
       ,commission
       ,ROW_NUMBER () OVER (ORDER BY commission NULLS FIRST) SNO
FROM employee;

We will get the following result:

Employee_Name Commission SNO
Emp D   1
Emp H   2
Emp G 10 3
Emp E 10 4
Emp F 10 5
Emp A 10 6
Emp C 20 7
Emp B 20 8

Here we can see that we have successfully fetched employees having no commission first in the list.

LAST Function in Oracle SQL – PLSQL

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The LAST Function in Oracle SQL / PLSQL is used to get the last value in an ordered set of records.

The LAST function can be used with the following functions.

  1. MIN()
  2. MAX()
  3. COUNT()
  4. SUM()
  5. AVG()
  6. STDDEV() and
  7. VARIANCE()

Syntax for using the LAST function in Oracle SQL / PLSQL is ;
SELECT
AGGREGATE_FUNCTION() KEEP (RANK_FUNCTION LAST ORDER BY AGGREGATE_FUNCTION(COLUMN))
FROM table_name
GROUP BY column(s);

Suppose we have a table named ‘employee’ as shown below:

Employee_ID Employee_Name Salary Department Commission
101 Emp A 10000 Sales 10
102 Emp B 20000 IT 20
103 Emp C 28000 IT 20
104 Emp D 30000 Support
105 Emp E 32000 Sales 10
106 Emp F 40000 Sales 10
107 Emp G 12000 Sales 10
108 Emp H 12000 Sales 10

Now, suppose we want to get the name of the department where the total salary being given is higher than total of salary in any other department, then we can achieve the same using LAST function as:

SELECT MAX(department) KEEP (DENSE_RANK LAST ORDER BY SUM(salary)) Max_Sal_Department
FROM employee
GROUP BY department;

We will get the following result:

MAX_SAL_DEPARTMENT
Sales

Here we can see that we have successfully fetched the name of the department in which the total salary is greater than total salary of any other department.

FIRST Function in Oracle SQL – PLSQL

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The FIRST Function in Oracle SQL / PLSQL is used to get the FIRST value in an ordered set of records.
The FIRST function can be used with the following functions.

  1. MIN()
  2. MAX()
  3. COUNT()
  4. SUM()
  5. AVG()
  6. STDDEV() and
  7. VARIANCE()

Syntax for using the FIRST function in Oracle SQL / PLSQL is ;
SELECT
AGGREGATE_FUNCTION() KEEP (RANK_FUNCTION FIRST ORDER BY AGGREGATE_FUNCTION(column))
FROM table
GROUP BY column(s);

Suppose we have a table named ‘employee’ as shown below:

Employee_ID Employee_Name Salary Department Commission
101 Emp A 10000 Sales 10
102 Emp B 20000 IT 20
103 Emp C 28000 IT 20
104 Emp D 30000 Support
105 Emp E 32000 Sales 10
106 Emp F 40000 Sales 10
107 Emp G 12000 Sales 10
108 Emp H 12000 Sales 10

Now, suppose we want to get the name of the department where the total salary being given is lesser than the total of salary in any other department, then we can achieve the same using FIRST function as:

SELECT MAX(department) KEEP (DENSE_RANK FIRST ORDER BY SUM(salary)) Min_Sal_Department
FROM employee
GROUP BY department;

We will get the following result:

MIN_SAL_DEPARTMENT
Support

Here we can see that we have successfully fetched the name of the department in which the total salary is lesser than total salary of any other department.

SQLCODE Function in Oracle SQL – PLSQL

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The SQLCODE Function in Oracle SQL / PLSQL is used to get the error number related with the latest generated exception.
The SQLCODE function should be used in the exception handling segment of the code.

A typical exception handling portion of code may look like;
EXCEPTION
WHEN exception_name1 THEN
[Statements / business logic]

WHEN exception_name2 THEN
[Statements / business logic]

WHEN exception_name3 THEN
[Statements / business logic]
.
.
WHEN exception_nameN THEN
[Statements / business logic]
END [procedure_name];

We can use the SQLCODE function to raise an error / exception as shown below.

EXCEPTION
WHEN OTHERS THEN
raise_application_error(-1001,'An error occurred: ' || SQLCODE || ' ERROR NUMBER:-' ||SQLERRM);
END;

We can also insert the error / exception in a database table as shown below:

 EXCEPTION
WHEN OTHERS THEN
  Error_code := SQLCODE;
  Error_message  := substr(SQLERRM,1,300);
INSERT INTO error_table(error_num, error_msg)
VALUES(error_number, error_message);
END;