Normalization is the process of minimizing redundancy and dependency by organizing fields and table of a database. The main aim of Normalization is to add, delete or modify field that can be made in a single table.
There are many ways to find second highest salary of Employees in SQ. You can either use SQL Join or Subquery to solve this problem.
Here is SQL query using Subquery :
Select MAX(Salary) from table1 WHERE Salary NOT IN ( select MAX(Salary)
Self-join is set to be query used to compare to itself. This is used to compare values in a column with other values in the same column in the same table. ALIAS ES can be used for the same table comparison.
TRUNCATE removes all the rows from the table, and it cannot be rolled back. DROP command removes a table from the database and operation cannot be rolled back.
A foreign key is one table which can be related to the primary key of another table. Relationship needs to be created between two tables by referencing foreign key with the primary key of another table.
Aggregate functions are used to evaluate mathematical calculation and return single values. This can be calculated from the columns in a table. Scalar functions return a single value based on the input value.
Aggregate – max(), count – Calculated with respect to numeric.
Scalar – UCASE(), NOW() – Calculated with respect to strings.
LIKE operator is used for pattern matching, and it can be used as -.
% – Matches zero or more characters.
_(Underscore) – Matching exactly one character.