SQL- Lecture 1 - Overview SQL Statement, Constraints, Create Table смотреть онлайн

Lecture Summary
*) SQL is not case sensitive. But, Data is case sensitive.
*) 0 is a digit. Space is a Character. NULL means unknown, inapplicable value.
*) Character and date must be enclosed within single quotation mark.

*Types of SQL Statement*
*DDL* - Data Definition Language
(CREATE, ALTER, DROP, TRUNCATE, RENAME)

*DML* - Data Manipulation Language
(INSERT, UPDATE, DELETE, MERGE)

*DCL* - Data Control Language
(GRANT, REVOKE)

*TCL* - Transaction Control Language
(COMMIT, ROLLBACK, SAVEPOINT)

*DQL* - Data Query Language
(SELECT)

*5 Types of Constraints*
*Primary Key* - Unique + Not Null
*Unique* - No Duplicate Allowed
*Not Null* - Null not Allowed
*Check* - To check validation
*Foreign Key* - Used for reference

*Column Level Constraint* defined at each column.
*Table Level constraints* defined after the definition of all columns are defined.

*Syntax Create Table*

CREATE TABLE table_name (
col1 datatype [column_constraint],
col2 datatype [column_constraint],
col3 datatype [column_constraint],
.
.
colN datatype [column_constraint],
[table_level_constraint]
)
/

*Example Create Table*

CREATE TABLE STUDENT(
RNO NUMBER(3) PRIMARY KEY,
NAME VARCHAR2(30) NOT NULL,
CITY VARCHAR2(30),
MOBILE UNIQUE
)
/

*1* RNO will always contain Unique value. RNO will not allow NULL value.
*2* NAME will not allow NULL value
*3* Mobile will not allow duplicate value.

*Syntax Insert Statement*
INSERT INTO table_name VALUES(col1_value, col2_value...)

*Example of Insert*
INSERT INTO STUDENT VALUES
(101, 'Ram', 'Rajkot', 9099090990)
/

Thank You

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