2. Yousuf Ibn Akhtar Sultan
SQL SERVER BASICS
SQL BASICS
CREATE statement – to create a new table
SYNTAX:
For creating a Database - CREATE DATABASE database_name
For creating a Table –
CREATE TABLE table_name
( column_name1 datatype,
Column_name2 datatype,
.
.
.
)
DROP statement – to drop a table
SYNTAX:
For deleting a table – DROP TABLE table_name
For deleting a database – DROP DATABASE database_name
TRUNCATING a Table – TRUNCATE TABLE table_name
Difference between DROP and TRUNCATE is that DROP is used to delete the entire table along with its
data whereas TRUNCATE is used to just delete the data from the table and the structure remains the
same.
ALTER statement – to add, delete or modify columns in a table
SYNTAX:
To add a column: ALTER TABLE table_name ADD column_name datatype
To delete a column: ALTER TABLE table_name DROP COLUMN column_name
To change data type: ALTER TABLE table_name ALTER COLUMN column_name datatype
To create a PRIMARY KEY after table has been created:
ALTER TABLE table_name
ADD PRIMARY KEY (column_name)
If you want to give a name for the primary key:
ALTER TABLE table_name
ADD CONSTRAINT primary_key_name
PRIMARY KEY (column_name)
To drop a PRIMARY KEY with a name: ALTER TABLE table_name
DROP CONSTRAINT primary_key_name
To create a FOREIGN KEY after the table has been created:
ALTER TABLE table_name
ADD FOREIGN KEY (column_name)
REFERENCES table_name(target_references_primary_key)
To create a FOREIGN KEY with a name: ALTER TABLE table_name
ADD CONSTRAINT foreign_key_name
FOREIGN KEY column_name
3. Yousuf Ibn Akhtar Sultan
SQL SERVER BASICS
REFERENCES table_name(target_references_primary_key)
To drop a FOREIGN KEY: ALTER TABLE table_name
DROP CONSTRAINT foreign_key_name
SP_HELP – to check the structure of the table, e.g, the column names, the data types, the constraints,
etc.
INSERT statements: used to INSERT data into table
SYNTAX:
INSERT INTO table_name VALUES (column1_value, column2_value,……., column’n’_value)
DELETE statements: used to DELETE a row from a table
SYNTAX:
DELETE FROM table_name
WHERE <condition/s>
To delete all data from a table
SYNTAX:
DELETE FROM table_name OR DELETE * FROM table_name
**This query has a similar functionality as TRUNCATE statement
UPDATE statements: used to update an existing record
SYNTAX:
UPDATE table_name
SET column1 = value, column2 = value, ……
WHERE <condition>
SELECT statements: used to select data from database. The result is stored in a result table, called as
result-set. There are different types of SELECTs
Type 1: (Simple SELECT without any conditions)
SYNTAX:
SELECT column_name/s
FROM table_name
If you want to see all the column names, you can either give all the column names in the SELECT clause
or use the following:
SELECT * FROM table_name
Type 2: SELECT DISTINCT – this would display only the distinct values if a column has a duplicate value.
SYNTAX:
SELECT DISTINCT column_name/s
FROM table_name
Type 3: SELECT statement with a WHERE clause – to extract those records depending on a condition
SYNTAX:
SELECT column_name/s
FROM table_name
WHERE <condition/s>
4. Yousuf Ibn Akhtar Sultan
SQL SERVER BASICS
Type 4: SELECT with ORDER BY clause – to sort the result-set by one or more columns
SYNTAX:
SELECT column/s
FROM table_name
WHERE <condition/s>
ORDER BY column_name/s ASC|DESC
*ASC – Ascending, DESC – Descending
** Default sorting order is ascending, if you don’t mention anything in the ORDER BY clause
Type 5: SELECT TOP – used to specify the number of records to return
SYNTAX:
SELECT TOP number|percent column_name
FROM table_name
Type 6: SELECT with LIKE operator – used to search for a specified pattern in a column
SYNTAX:
SELECT column_name/s
FROM table_name
WHERE column_name LIKE pattern
e.g.
SELECT *
FROM contact
WHERE name LIKE ‘S%’ – this would return all contacts whose name begins with S
Type 7: SELECT with IN operator – allows to specify multiple values in the WHERE clause
SYNTAX:
SELECT column_name/s
FROM table_name
WHERE column_name IN (value/s)
e.g
SELECT *
FROM contact
WHERE city IN (‘Kalimpong’,’Kolkata’) – this would return all contacts who are from the cities
Kalimpong and Kolkata
Type 8: SELECT with BETWEEN operator – this selects a value within a range. The values can be number,
text or dates
SYNTAX:
SELECT column_name/s
FROM table_name
WHERE column_name BETWEEN value1 AND value2
e.g.
SELECT *
FROM products
WHERE price BETWEEN 50 AND 150
5. Yousuf Ibn Akhtar Sultan
SQL SERVER BASICS
NOT BETWEEN operator
e.g.
SELECT * FROM products WHERE price NOT BETWEEN 50 AND 150
BETWEEN operator with IN
e.g.
SELECT * FROM products
WHERE (price BETWEEN 10 AND 20) AND NOT categoryID NOT IN (1,2,3)
Aggregate Functions
• AVG() – returns the average value
• COUNT() – returns the number of rows
• MAX() – returns the largest value
• MIN() – returns the smallest value
• SUM() – returns the sum
SELECT with GROUP BY clause – used along with the aggregate functions to group the result set by one
or more columns
SYNTAX:
SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE <condition>
GROUP BY column_name
e.g.
SELECT deptno,count(deptno)
FROM emp
GROUP BY deptno
SELECT with HAVING clause – it is used as a filter to the GROUP BY clause and it cannot be used without
an aggregate function
SYNTAX:
SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE <condition/s>
GROUP BY column_name
HAVING aggregate_function(column_name) operator value
e.g.
SELECT deptno,count(deptno)
FROM emp
GROUP BY deptno
HAVING count(deptno) > 4
6. Yousuf Ibn Akhtar Sultan
SQL SERVER BASICS
SELECT INTO statement – used to copy information from one table to another. It copies data from one
table and inserts into a new table
SYNTAX:
SELECT column_name/s
INTO new_table_name
FROM old_table_name
Eg.
SELECT *
INTO emp_new
FROM emp
INSERT INTO statement – used to copy columns from one table to another existing table
SYNTAX:
INSERT INTO table2_name
SELECT column_name/s FROM table1_name
NOT NULL constraint – it enforces a column NOT to accept a NULL value
UNIQUE constraint – it uniquely identifies each record in a database table
ALTER TABLE table_name ADD CONSTRAINT constraint_name UNIQUE (column_name/s)
ALTER TABLE table_name ADD CONSTRAINT constraint_name
CHECK constraint – is used to limit the range value that can be placed in a column
e.g
CREATE TABLE persons
( p_id int,
Last_name varchar(30),
First_name varchar(30),
Gender varchar(1),
CHECK (Gender IN (‘M’,’F’)))
ALTER TABLE table_name
ADD CHECK (condition/s)
ALTER TABLE table_name
ADD CONSTRAINT constraint_name CHECK (condition/s)
ALTER TABLE table_name
DROP CONSTRAINT constraint_name
To check the structure of a table: SP_HELP table_name
To check the tables in a database: SELECT name FROM sys.tables
SQL syntax to get an output using ESCAPE clause
E.g. if you want to get a output from a table where a name has a ‘%’ symbol in it.
SYNTAX: SELECT * FROM emp
WHERE ename LIKE (‘%%%’) ESCAPE ‘’
7. Yousuf Ibn Akhtar Sultan
SQL SERVER BASICS
JOINS
SQL JOIN is used to combine rows from two or more tables based on the common column field between
them.
The different types of JOINs are: -
I) INNER JOIN: Returns all rows when there is at least one match in BOTH tables
II) LEFT OUTER JOIN: Return all rows from the left table, and the matched rows from the right
table
III) RIGHT OUTER JOIN: Return all rows from the right table, and the matched rows from the
left table
IV) FULL OUTER JOIN: Return all rows when there is a match in ONE of the tables
INNER JOIN: selects all rows from both tables as long as there is a match between the columns in both
tables.
SYNTAX FOR INNER JOIN:
SELECT column_name/s
FROM table1 INNER JOIN table2
WHERE table1.column_name = table2.column_name
LEFT OUTER JOIN: returns all rows from the left table (table1), with the matching rows in the right table
(table2). The result is NULL in the right side when there is no match.
SYNTAX FOR LEFT OUTER JOIN:
SELECT column_name/s
FROM table1 LEFT OUTER JOIN table2
WHERE table1.column_name = table2.column_name
RIGHT OUTER JOIN: returns all rows from the right table (table2), with the matching rows in the left
table (table1). The result is NULL in the left side when there is no match.
SYNTAX FOR RIGHT OUTER JOIN:
SELECT column_name/s
FROM table1 RIGHT OUTER JOIN table2
WHERE table1.column_name = table2.column_name
FULL OUTER JOIN: returns all rows from the left table (table1) and from the right table (table2). The
FULL OUTER JOIN keyword combines the result of both LEFT and RIGHT joins.
SYNTAX FOR FULL OUTER JOIN:
SELECT column_name/s
FROM table1 FULL OUTER JOIN table2
WHERE table1.column_name = table2.column_name
UNION: is used to combine the result-set of two or more SELECT statements. Notice that each SELECT
statement within the UNION must have the same number of columns. The columns must also have
similar data types. Also, the columns in each SELECT statement must be in the same order.
SYNTAX FOR UNION:
SELECT column_name/s FROM table1
UNION
SELECT column_name/s FROM table2
8. Yousuf Ibn Akhtar Sultan
SQL SERVER BASICS
VIEWS
In SQL, a view is a virtual table based on the result-set of an SQL statement.
A view contains rows and columns, just like a real table. The fields in a view are fields from one or more
real tables in the database.
You can add SQL functions, WHERE, and JOIN statements to a view and present the data as if the data
were coming from one single table.
SYNTAX FOR CREATING A VIEW:
CREATE VIEW view_name AS
SELECT statement
SYNTAX FOR DROPPING A VIEW:
DROP VIEW view_name
SYNONYM
Synonyms are objects in SQL Server that gives an Alias name to a table or a view. There happens
sometimes that the table names are very long and difficult to remember, in such cases we can give an
Alias name for the table using Synonyms.
SYNTAX FOR CREATING A SYNONYM:
CREATE [PUBLIC/PRIVATE] SYNONYM new_name FOR old_name
To Re-name a table:
SP_RENAME ‘old_table_name’ ’new_table_name’
To Re-name a column:
SP_RENAME ‘table_name.column_name’ ‘new_column_name’
