SQL Server Accessing data interview questions
SQL Server data integrity - Nov 18, 2008 at 18:00 PM by
Rajmeet Ghai
Explain the full syntax of Select Statement with examples.
Answer
SELECT is used to select a specific or ALL columns / rows from a
table.
Syntax:
SELECT list_columns FROM table_name
List_columns are the columns to be selected to retrieve the rows. While
table_name is the table from which these columns needs to be selected. Many
clauses can be added to this SELECT statement.
Example 1: Displays rows with customers balance between 10 and 10000
SELECT first_name FROM Customer WHERE cust_bal BETEEN 10 and 10000;
Example 2: Sort the names in an ascending order
SELECT first_name FROM Customer ORDER BY first_name;
Explain some of the keywords of Select Statement like Distinct Keyword, Top n
Keyword with an example for each of them.
Answer
DISTINCT: Distinct clause helps to remove duplicates and returns a
result set.
Syntax: DISTINCT (set_expression)
Example:
Select DISTINCT company_name FROM Company;
TOP N: returns the top “n” records from a table.
Syntax : TOP N
Example:
Select TOP 10 Cust_name from Customer;
Describe the use of Into and From clause with examples.
Answer
INTO: The INTO keyword inserts data from one table into another. It is
commonly used in SELECT statement. It is useful in creating back ups.
SYNTAX:
SELECT * INTO new_table FROM old_table
Example: Copy all columns from table customer into customer_backup
SELECT * INTO Customer_backup FROM customer
FROM: the FROM clause selects rows from the table specified.
Syntax:
SELECT * FROM table_name
Example: Select all columns from a table customer
SELECT * FROM Customer
Describe where, group by and having clause with examples for each of them.
Answer
WHERE: Where clause in a SELECT query is used to retrieve specific
records that meet the specified criteria.
SYNTAX:
SELECT column_name FROM Table_name WHERE predicate
Example: to display customers with first name is john
Select first_name From customer Where first_name =’john’;
GROUP BY: Group By clause in select statement is used to group or collect data
of multiple records of one ore more columns.
SYNTAX: SELECT column_name FROM table_name WHERE predicate GROUP BY column1,
column2..;
Example: To Group records by city SELECT city_name FROM Customer GROUP BY city;
HAVING: The HAVING clause is used to filter records that have been grouped using
GROUP BY clause. Hence HAVING clause is used with GROUP BY.
Syntax: SELECT column_name FROM table_name WHERE predicates GROUP BY column1,..
HAVING condition1…
Example: To Group records by employee with salary > 10000 SELECT emp_name
FROM employee GROUP BY emp_name HAVING salary > 1000;
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Describe the use of Into and From clause with examples.
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