BI Developer: 2018

What is Primary Key in SQL Server?

PRIMARY KEY

1. It's a CONSTRAINT, a collection of columns uniquely identifies each row in a table

2. Only one PRIMARY KEY constraint allows on Table.

3. PRIMARY KEY column will not allow NULL Values & duplicate values

What is the difference between DELETE and TRUNCATE statements?

TRUNCATE vs DELETE

TRUNCATE	DELETE
Truncate is used to delete the all records in table	Delete is used to delete the row level and table level data
We can’t rollback the data	We can rollback data if we maintain the transaction
It’s auto committed	It’s explicit committed
It’s a DDL (Data Definition Language) Command	It’s a DML (Data Manipulation Language) Command
It’s faster than the delete	It’s very slow when we compare with TRUNCATE

Synchronous and Asynchronous Transformations In SSIS

I am going to explain in simple manner about Synchronous and Asynchronous Transformations in SSIS, as we know in SSIS everything based on transformations only, so these divided into few types.

Synchronous and

Asynchronous

Mostly we should prefer for Synchronous only when we are not able to meet our requirements using Synchronous then only we should go for Asynchronous Transformation.

Synchronous (non-blocking):

Processing the row by row transformation into next task, in detail, one record will not wait /depend on buffer for other record, example Data Conversion Transformation, DCT will not wait / depend on other record to transform to the next task simply it will convert the record and send to the next task, so Output is Synchronous with Input.

Asynchronous(Fully Blocking):

Processing rows will depend on other / next record based on those next record it will take the decision and transform to the next task, Example, Sort Transformation, in this transformation holds the all records on buffer then it will make the decision based on the data then only records will pass to the next task.

More about these Transformation please go through below link(s).

Understanding Synchronous and Asynchronous Transformations

Please give your valuable comments below :)

Ways of column alias name in SQL Server.

As per my knowledge I am using in three ways of giving alias names to the database table column in SQL Server while selecting,

Below are the types which I am using:

1. Giving the alias name in Square Bracket [ ]

2. Giving the alias name with Underscore _

3. Giving the alias name with Double Quotes “ ”

4. Giving Direct Expected Name

1. Square Brackets

The required column/ header name should be with in the Square Brackets only, with in this bracket we can give spaces also in expected name, so mostly we will use these kinds of brackets when we have space in our expected column name, below is the example.

Example:

SELECT

Empno --Original Name of the column

, Empno AS [Employee Number]--Alias Name of the Column FROM tbl_Emp

O/P

2. Underscore _

The required column/ header name should be with Underscore i.e. _, with this underscore only between the two words like Employee and Name, we have to concatenate these two with Underscore I.e. Employee_Name

Example:

SELECT

Empno --Original Name of the column

, Empno AS Employee_Number --Alias Name of the Column FROM tbl_Em

O/P

3. Double Quotes:

The required column/ header name should be within the Double Quotes only, with in this double quote we can give spaces also in expected column name, so this also mostly we will use these kinds of Quotes when we have spaces in our expected column name, below is the example.

Example:

SELECT

Empno --Original Name of the column

, Empno AS "Employee Number"--Alias Name of the Column FROM tbl_Emp

O/P

4. Direct Expected Name:

This like directly whatever you what you can give, there is no such condition like above, but here we can’t write column name with spaces, it will work only for single world column name

Example:

SELECT

Empno --Original Name of the column

, Empno AS "EmployeeNumber"--Alias Name of the Column

FROM tbl_Emp

O/P

Please comment below

Department (Dept) Sample Data

Please Copy the below Query and run on your SSMS.

/* Droping the Existing Dept Table: */
DROP TABLE IF EXISTS tbl_Dept;

/* Creating New Dept Table: */
CREATE TABLE tbl_Dept(
tbl_Deptno INT NOT NULL PRIMARY KEY
, DName VARCHAR(50) NOT NULL
, Location VARCHAR(50) NOT NULL);

/* Inserting Data into Dept Table: */
INSERT INTO tbl_Dept VALUES
(10,'Accounting','New York')
,(20,'Research','Dallas')
,(30,'Sales','Chicago')
,(40,'Operations','Boston');

/*cSeleting Inserted Data */
SELECT * FROM tbl_Dept

Click Here for : Employee Table Sample Data

Please comment below

Employee (Emp) Sample Data

Please Copy the below Query and run on your SSMS.

/*Please relook once you before Drop the Existing Table: */
DROP TABLE IF EXISTS tbl_Emp;

/*Creating New Employee Table*/
CREATE TABLE tbl_Emp(
Empno INT NOT NULL PRIMARY KEY
, Ename VARCHAR(50) NOT NULL
, Job VARCHAR(50) NOT NULL
, Mgr INT
, Hiredate DATE
, Sal DECIMAL(10,2)
, Comm DECIMAL(10,2)
, Deptno INT NOT NULL);

/*Inserting Data Into above created Table: */
INSERT INTO tbl_Emp (Empno,Ename,Job,Mgr,Hiredate,Sal,Comm,Deptno)
VALUES
(7369, 'SMITH', 'CLERK', 7902, '6/13/93', 800, 0.00, 20)
, (7499, 'ALLEN', 'SALESMAN', 7698, '8/15/98', 1600, 300, 30)
, (7521, 'WARD', 'SALESMAN', 7698, '3/26/96', 1250, 500, 30)
, (7566, 'JONES', 'MANAGER', 7839, '10/31/95', 2975, null, 20)
, (7698, 'BLAKE', 'MANAGER', 7839, '6/11/92', 2850, null, 30)
, (7782, 'CLARK', 'MANAGER', 7839, '5/14/93', 2450, null, 10)
, (7788, 'SCOTT', 'ANALYST', 7566, '3/5/96', 3000, null, 20)
, (7839, 'KING', 'PRESIDENT', null, '6/9/90', 5000, 0, 10)
, (7844, 'TURNER', 'SALESMAN', 7698, '6/4/95', 1500, 0, 30)
, (7876, 'ADAMS', 'CLERK', 7788, '6/4/99', 1100, null, 20)
, (7900, 'JAMES', 'CLERK', 7698, '6/23/00', 950, null, 30)
, (7934, 'MILLER', 'CLERK', 7782, '1/21/00', 1300, null, 10)
, (7902, 'FORD', 'ANALYST', 7566, '12/5/97', 3000, null, 20)
, (7654, 'MARTIN', 'SALESMAN', 7698, '12/5/98', 1250, 1400, 30);

/*Selecting Data from Table*/
select * from tbl_Emp

Please comment below