Topic 1: Introduction to SQL

SQL stands for Structured Query Language. SQL is a standard computer language for accessing and manipulating databases SQL is the set of commands that is recognized by nearly all RDBMS.

SQL commands can be divided into following categories. Data Definition Language (DDL) Data Manipulation Language (DML) Transaction Control Language (TCL)

DDL (Data Definition Language) Commands: These commands are used for creation; alteration and removal of database objects e.g.: CREATE TABLE, ALTER TABLE, and DROP TABLE.

DML (Data Manipulation Language) Commands: These commands are used to add, modify or remove the data contained in the database tables. e.g.: INSERT, DELETE, UPDATE, SELECT etc. are DML commands.

TCL (Transaction Control Language) Commands These commands are used to start or end transactions. e.g.: COMMIT, ROLLBACK, ROLL BACK TO etc. are TCL commands.

Topic 2: DDL commands Note: All commands given below are based on the table Student: Table: Student CREATE is used to create a table. The syntax of this command is: create table tablename(column1name datatype [constraint],column2name datatype [constraint], column3name datatype [constraint]);

Keywords specifying Items that may be created table Data Types char(size) - Fixed length string of characters of the set size. The size of the string is limited to 255 characters. date number(maxsize) - Number with a maximum number of digits specified by "maxsize". number(maxdigits,maxright) - A decimal number with a manimum number of "maxdigits" with "a maximum number of digits to the right of the decimal, "maxright". varchar(maxsize) - A character string with variable lingth limited to "maxsize". Constraints Constraints are rules for the column.. Possible values include: not null - The column values must have a value and cannot be null. primary key - Each record is uniquely identified by this column. unique - No two values may be the same in the column

Example create table citylist(name varchar(20),state varchar(20),population number(8),zipcode number(5) unique);

STUDENT NameRollClassAgeMarks Raghav101C Ajay102M Gagan103C Shika104E121485

Delete table: Drop table name Example drop student;

Topic 3:DML command INSERT INTO: A row or tuple can be inserted in an existing table with the help of an INSERT command.It is DML command Syntax: Insert into tablename [column list] values (val1, val2,…) Note: Values should be inserted in the same order as table creation.

Example: Write a command to insert a row in the table student. Ans: Insert into student values (‘ahmed’, 105, C12, 16, 98);

UPDATE STATEMENT: Update command is used to make changes to the existing values.

Example 1: Write a command to change the marks from 40 to 86 for rollno 2 Ans: Update Student Set marks =86 where rollno = 2;

Example 2: Write a query to change the marks as 95 and grade a A+ for rollno 31. Ans: Update Student set marks=95 and grade=’A+’ where rollno = 31;

Example 3: Write a command to update all the marks by adding 5 marks for all students. Ans: Update Student set marks = marks +5;

Example 4: Write a command to change the grade as A for all students whose marks is greater than 90. Ans: Update Student set grade=’A’ where marks > 90;

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DELETE COMMAND: This command is used to delete one row or more than one row. Example: Write a command to delete the details of students who have scored less than 33 marks. Ans: Delete from Student where marks < 33;

SELECT: The SELECT statement is used to select data from a table. The tabular result is stored in a result table (called the result-set). Syntax: SELECT [ALL | DISTINCT] columnname1 [,columnname2]FROM tablename1 [,tablename2][WHERE condition] [ and|or condition...][GROUP BY column-list][HAVING "conditions][ORDER BY "column-list" [ASC | DESC] ] Note: SQL statements are not case sensitive. SELECT is the same as select.

Example 1: Select * from student; Example 2: Select all from student; The above two commands display all the details from the table Student. Example 3: Select name, marks from student; This command will display only the name & marks columns from the table student. Example 4: Select Distinct class from student;

DISTINCT can be used to select column names and values deleting duplicates. Output: Class C12 M12 E12

WHERE clause: The WHERE clause is used to specify a selection criterion. To conditionally select data from a table, a WHERE clause can be added to the SELECT statement.

Syntax SELECT column FROM table WHERE column operator value

With the WHERE clause, the following operators can be used: OperatorDescription =Equal <>Not equal >Greater than <Less than >=Greater than or equal

<= Less than or equal BETWEEN Between an inclusive range LIKE Search for a pattern IN If you know the exact value you want to return for at least one of the columns

Example 1: Select name, marks from student where age > 14; NameMarks Raghav90 Gagan90

Example 2: Write a query to display all details about the students whose age is 15. Ans: Select * from Student where age=15;

Example 3: Write a query to display name, roll and class of all students whose marks is above 90. Ans: Select name, roll, class from Student where marks > 90;

Example 4: Write a query to display the name and age of students who belong to class C12. Ans: Select name, age from student where class = ‘C12’;