The data is stored in the tables in relational database management systems. In order to retrieve data from tables, we use SQL SELECT statement.

The MS SQL CONVERT function enables us changing the data type of expression from one to another. For example:
SELECT CONVERT(varchar, 50.55);

In the case of SQL Server, the IF statement is used to execute SQL statements if a condition is TRUE.
For example: IF @table_name = ’employees’

For returning the date part in a date e.g. day, month, year, hour, minute, second, day of year etc., use the SQL DATEPART function. The DATEPART function takes two arguments, for example:

The SQL LEFT JOIN fetches all the records from the left table and only matched records from the right table.

The IFNULL function replaces the NULL values by given expression. For example:
SELECT IFNULL(NULL, “alt_val”) AS “Alternative Value”;

For populating new data into the SQL database tables, you may use the INSERT INTO statement. The SQL INSERT INTO statement allows you entering the data in two ways.

The SQL DELETE command is used to remove the records from the relational database tables permanently. For example: DELETE FROM table_name;

The “OR” is a logical operator in SQL that is used to combine two or more conditions in the WHERE clause. The WHERE clause with OR operator can be used with SELECT, UPDATE, INSERT and DELETE statements.

The IN operator enables you providing a list of values to be tested in the WHERE clause (generally) with SELECT, DELETE, or UPDTAE statements.

The simple SELECT statement returns all records from the table(s) in an SQL database. For example: SELECT * FROM tbl_name; In order to return only filtered records or rows that fulfill certain criteria, the SQL WHERE clause is used in…

You may use SQL CAST and CONVERT functions for converting int to string and vice versa. Both these functions are little different to use.

In MS SQL Server, the DATEDIFF function is used to get the difference between two dates in terms of years, months, days, hours, minutes. e.g. SELECT DATEDIFF(day, ‘2018-03-13’, GETDATE()) AS “Difference in days”;

The SQL ISNULL function enables you replacing the NULL values with the specified value as retrieving data from the SQL Server database.

The SQL GETDATE function returns the current date and time. For example: SELECT GETDATE() AS “Date & Time”;