SDE - 1

Data integrity is the overall accuracy, completeness, and consistency of data. Data integrity also refers to the safety of data in regard to regulatory compliance — such as GDPR compliance — and security. It is maintained by a collection of processes, rules, and standards implemented during the design phase. When the integrity of data is secure, the information stored in a database will remain complete, accurate, and reliable no matter how long it’s stored or how often it’s accessed.

A trigger is a stored procedure in database which automatically invokes whenever a special event in the database occurs. For example, a trigger can be invoked when a row is inserted into a specified table or when certain table columns are being updated.

Syntax:
create trigger [trigger_name] 
[before | after] 
{insert | update | delete} 
on [table_name] 
[for each row] 
[trigger_body] 

Explanation of syntax:
create trigger [trigger_name]: Creates or replaces an existing trigger with the trigger_name.
[before | after]: This specifies when the trigger will be executed.
{insert | update | delete}: This specifies the DML operation.
on [table_name]: This specifies the name of the table associated with the trigger.
[for each row]: This specifies a row-level trigger, i.e., the trigger will be executed for each row being affected.
[trigger_body]: This provides the operation to be performed as trigger is fired

1. There can be only one clustered index per table. However, you can create multiple non-clustered indexes on a single table.
2. Clustered indexes only sort tables. Therefore, they do not consume extra storage. Non-clustered indexes are stored in a separate place from the actual table claiming more storage space.
3. Clustered indexes are faster than non-clustered indexes since they don’t involve any extra lookup step.

The only difference between Union and Union All is that Union extracts the rows that are being specified in the query while Union All extracts all the rows including the duplicates (repeated values) from both the queries.

The major function of a cursor is to retrieve data, one row at a time, from a result set, unlike the SQL commands which operate on all the rows in the result set at one time. Cursors are used when the user needs to update records in a singleton fashion or in a row by row manner, in a database table.

TOP keyword can be used to find the nth highest salary. By default ORDER BY clause print rows in ascending order, since we need the highest salary at the top, we have used ORDER BY DESC, which will display salaries in descending order. Again DISTINCT is used to remove duplicates. The outer query will then pick the topmost salary, which would be your Nth highest salary.

SQL query : 
SELECT TOP 1 salary
FROM ( 
SELECT DISTINCT TOP N salary
FROM #Employee 
ORDER BY salary DESC 
) AS temp
ORDER BY salary

Tip 1 : The cross questioning can go intense some time, think before you speak.

Tip 2 : Be open minded and answer whatever you are thinking, in these rounds I feel it is important to have opinion.

Tip 3 : Context of questions can be switched, pay attention to the details. It is okay to ask questions in these round, like what are the projects currently the company is investing, which team you are mentoring. How all is the work environment etc.