Tag Archives: T-SQL

ByHariharan Rajendran

Generate SELECT Statement

This article explains that how to generate SELECT statement with all the table columns.

In the Production environment, most of the tables will have more than 100 columns. If those tables are used in a report with all the columns then it will be difficult to type all the columns.

To ease the process, we can generate the SELECT statement and can use that for any purpose.

Use the below code and pass the table which you want to use in the SELECT statement.

In this example, I used FactInternetSales table.

—–Code——-

Declare @Column varchar(500), @tableName varchar(25)

SET @tableName =’FactInternetSales’

SET @Column = ”

select @Column = @Column + Column_Name + ‘, ‘ from [AdventureWorksDW2014].INFORMATION_SCHEMA.COLUMNS

where table_name=@tableName

select ‘SELECT ‘ + SUBSTRING(@Column, 0, LEN(@Column)) + ‘ From ‘+@tableName as SELECTScript

—–Code———-

SQL1

Copy and paste the result and execute the script.

SQL2

ByHariharan Rajendran

T-SQL Basics – Day 1

If you are reading this article then you are looking an very easy way to understand the T-SQL Scripts.

Let us learn T-SQL with a scenario, consider you have a sheet with some employee information. Your boss asking questions from that sheet and you need to answer him. In simple, your task is “Read from Sheet”.

Convert the general words into technical terms,

Sheet – Table (Employee) in a Database

Questions – T-SQL Statement

Answer – Output of T-SQL

Read – Select

Read from Sheet – Select from Table

If you are familiar with above terms then you can easily learn T-SQL Statements.

Let’s start,

Boss: What are the information available of an employee?

You: Read all the field name from Sheet

Tab1

T-SQL: SELECT * FROM Employee

Tab17

Note: “*” denotes all the fields from a table.

Boss: Do we have employee Name, Age & Country?

You: Yes

Tab2

T-SQL: SELECT Name, Age, Country FROM Employee

Tab18

Boss: What is the age of Richard? Or what is the country name of Richard?

You: 42 or UK

Tab3

T-SQL: SELECT * FROM Employee Where Name=’Richard’

Tab13

Note: Need to use WHERE keyword when we say specific data.

Boss: Who are all crossed age 40?

You: Read from sheet

Tab4

T-SQL: SELECT * FROM Employee WHERE Age > 40

Tab14

Note: Need to use WHERE keyword when we say specific data.

Boss: Whose names start with letter K?

You: Read from sheet

Tab5

T-SQL: SELECT * FROM Employee WHERE Name LIKE ‘K_%’

Tab15

Note: Need to use WHERE keyword when we say specific data. Use LIKE keyword when you want to play with the letters or pattern in a value. There are few other patterns available for LIKE which will discuss in the next article.

Boss: Convert the values of a Marital Status column into detailed values.

You: Add a new column

Tab6

T-SQL: SELECT *, CASE WHEN [Marital Status] =’M’ THEN ‘Married’ ELSE ‘UnMarried’ End MStatus FROM Employee  

Tab16

Note: Use “CASE WHEN XXXX THEN XXXXX ELSE XXXXX END” Syntax when you want derive something. We can discuss the detailed version above syntax in next article.

 

ByHariharan Rajendran

Database Table and Primary Key – Part 1

Creating a table in MS SQL Server is very easy, this can be achieved by using T-SQL scripts or GUI. This article will use T-SQL Scripts to a create a table.

Basic Pre-Requisites to create a table,

  1. Understand the purpose of the table
  2. Identify the columns and data types. Refer this link, to know about data types.

Table is the storage unit in a database which stores the data in rows and columns as like excel sheet. The output of the table result is similar to the excel sheet data.

If you are decided to store some data in a database then you must use table.

The basic table structure will look like below.

CREATE TABLE Users

(Id int)

We can add more columns in the structure, each column should be define with the right data type. Here Id is the column name and int is the data type which is nothing but an integer.

Let us discuss, what is a primary key and how to create it.

Primary key is a constraint which we need to define in any one of the column in a table. It will not allow null values in that defined column and entry to the column should be unique  i.e. it won’t allow duplicate values.

Choose an ID or Unique Identifier (GUID) column to create a primary key, this is the best way to define a table structure.

Create a table with primary Key on integer column,

CREATE TABLE Users

(Id int primary key,

Name varchar(50))

In the above script, ID column is considered as a primary key. You can check this by clicking the columns folder under dbo.Users table.

Create a table with primary key on unique identifier column,

CREATE TABLE Users

( Id uniqueidentifier primary key,

Name varchar(50))

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