What is Checking a Database?

A database is nothing but a structured data array that includes data storage and helps to manipulate data. Database checking refers to the testing of the data we have collected in the database. We need to check the data in the database and ensure that the right data set is stored in the tables of the database according to the user’s knowledge.

Need For Database testing:

The database is a data dump where the data is gathered in an immense quantity and stored in a standardized format. Since the DataBase Management System offers a structured way for this information to be handled, collected and stored, there are occasions when records can become obsolete, duplicated, etc. Database verification falls into the picture in such situations, which allows one to verify. There are four data authentication types.

1. Data Mapping- This applies to data filtering, i.e. the same data should be stored in the database that is entered at the frontend by the user.

2. ACID Properties– ACID stands for Atomicity, Toughness, Separation and Consistency. Validation of all four properties helps to protect data stability, stability, and safety.

3. Data Consistency- If either of the CRUD (Create, Retrieve, Upgrade, and Delete) operations change the data, the current information on each and every UI should be displayed.

4. Complex database- It applies to complex elements such as restrictions, stored protocols, causes, etc. Market law enforcement Thus, to verify these dynamic elements, it is the responsibility of the tester to better SQL queries.

Importance of SQL for DB testing:

Database testing with SQL Each second, an enormous amount of data is generated. SQL offers a standard way to tackle this sort of knowledge. The Standard Query Language (SQL) is pronounced as “S-Q-L” or occasionally as “See-Quel,” and is the traditional Relational Databases language. SQL is used for importing, checking, reviewing, deleting, changing database information.

Essentially, there are two types of SQL commands:

1. DDL(Data Description Language) – This refers to a series of SQL commands, including indexes, triggers, tables, and displays, that can construct and manipulate database structures. To build a database schema, DDL commands are used to describe the form and structure of the data to be contained in a database. 

• Create
• Drop 
• Truncate 
• Alter

2. DML(Data Manipulation Language) – This applies to the database manipulation suite of SQL commands. The embedded DML is used for general programming languages. 

• Insert Into 
• Update 
• Delete 
• Select

Basic Queries using SQL Commands:

1. SELECT

The SELECT  statement is used to select the data from the tables present in the Database. It provides data from a particular table. It’s a DML command.

We can also use the SELECT keyword with  DISTINCT, ORDER BY, GROUP BY, HAVING Clause and INTO.

SELECT TempID, TempName

FROM Temp;

(*) is used to select all the data from a particular table

SELECT * FROM Temp;

SELECT TOP 3 * FROM Temp;

2. DROP Table

It is used to drop the table i.e table will be deleted permanently from the database and also data present inside the table.

DROP TABLE Temp;

3. UPDATE

The UPDATE statement is used to update and modify the existing records present in the table. It’s a DML command.

UPDATE Temp

SET TempName = 'Raks', City= 'Ghaziabad'

WHERE TempID = 2;

4. TRUNCATE

The TRUNCATE statement is used to delete the data present inside the table i.e. the data inside the table will be completely lost but the table will remain there in the database.

TRUNCATE Table Temp;

5. LIKE

LIKE  is used with WHERE clause to search for a specified pattern in a column of a table.

SELECT * FROM Temp

WHERE TempName LIKE 'T%';

6. INSERT INTO

The INSERT INTO statement is used to insert the new records in a particular table. It’s a DML command.

INSERT INTO TableName (Column1, Column2, Column3, ...,ColumnN)

VALUES (value1, value2, value3, ...);

–If you do not want to mention the column name, but the order of values entered should match the column data types :

INSERT INTO TableName

VALUES (Value1, Value2, Value3, ...);

7. ALTER TABLE

ALTER is used to delete, add, modify columns of the existing table. We can also use alter with ADD and DROP to add or drop any particular column in the table. We can also use the alter with UPDATE for modifying any particular column in the table.

ADD Column Gender;

Alter table TEMP;

ADD Gender varchar (255);

8. DELETE

This assertion is included in every particular table to delete the current records available. It’s a command from DML.

DELETE From Temp Where TempName = ‘Raks’;

9. ORDER BY

This declaration is used in order to group the results in an ascending or descending order. By default, results are in ascending order and represent the outcomes in descending order the Desc keyword should be used.

SELECT From Temp Order By TempId;

10. GROUP BY

For the aggregate functions, the GROUP BY argument is used to group the result set by one or more columns.

SELECT Count (TempId), City  

From Temp   

Group By City

SQL Joins:

Centred on a linked column between such tables, JOINS are used to merge rows from two or more tables. They are mainly used when a user tries to retrieve data from tables that have one-to-many or many-to-many relationships between them. There are four kinds of entries:

1. INNER Join: Returns all records in both tables which have corresponding values.

2. FULL Join: Returns all documents that match either the left or right table of the table.

3. LEFT Join: This returns all records from the left table and the records from the right table that satisfy the requirement.

4. RIGHT Join: Returns all records and information from the Right Table and the records from the left table that satisfy the requirement.