This document describes SQL commands for data definition language (DDL) and data manipulation language (DML) in Oracle. It outlines commands to create, alter, and delete tables as well as insert, select, update, and delete data. Table and column names must follow identifier rules where the first character is a letter and subsequent characters can be letters, numbers, or underscores.

1. SQL(Oracle) Queries
DDL (Data definition language)
TABLE
Create table CREATE TABLE<table_name>
(< column_name1> <datatype> [<constraint>],
< column_name2> <datatype> [<constraint>],…);
Show tables list Select * from TAB;
Describe table(table structure) DESCRIBE <table_name>;
Delete/Drop table DROP TABLE <table_name>;
Rename table RENAME <old_table_name>TO <new_table_name>;
Add a column ALTER TABLE <table name>
ADD <new_column_name> <datatype> [<constraint>];
Rename a column ALTER TABLE <table name>
RENAME COLUMN <old_column_name> TO
<new_column_name>;
Delete a column ALTER TABLE <table name>
DROP <column_name>;
Modify datatype or
size
ALTER TABLE <table name>
MODIFY <column_name> <datatype> [<constraint>];
COLUMN
CONSTRAINTS
Constraints Add constraint Drop constraint
Not null ALTER TABLE <table name>
MODIFY <column_name>
CONSTRAINT <constraint_name>NOT NULL;;
ALTER TABLE <table name> MODIFY
<column_name> NULL;
Unique ALTER TABLE <table name>
ADD CONSTRAINT <constraint_name>
UNIQUE (<column_name>);
ALTER TABLE <table name>
DROP CONSTRAINT
<constraint_name>;
Check ALTER TABLE <table name>
ADD CONSTRAINT <constraint_name>
CHECK (<column_name><condition>);
ALTER TABLE <table name>
DROP CONSTRAINT
<constraint_name>;
Primary
key
ALTER TABLE <table name>
ADD CONSTRAINT <constraint_name>
PRIMARY KEY (<column_name>);
ALTER TABLE <table name>
DROP CONSTRAINT
<constraint_name>;
Default ALTER TABLE <table name>
MODIFY <column_name> DEFAULT <value>;
ALTER TABLE <table name>
MODIFY <column_name> DEFAULT
NULL;
Foreign key ALTER TABLE <table name>
ADD CONSTRAINT <constraint_name>
FOREIGN KEY (<column_name> )
REFERENCES <table name1> (<column_name> );
ALTER TABLE <table name>
DROP CONSTRAINT
<constraint_name>;

2. DML (Data Manipulation language)
INSERT
Insert into all columns INSERT INTO <table_name>
VALUES (<column1_value>,< column2_value>,……);
Insert into specific columns INSERT INTO <table_name> (<column1>, <column2>,…)
VALUES (<column1_value>, <column2_value>,……);
SELECT
Select all data (all rows all columns – full
table)
SELECT *
FROM <table_name>;
Select specific columns SELECT <column1, column2,….>
FROM <table_name>;
Select all data based on condition SELECT *
FROM <table_name> WHERE<condition>;
Select data in ascending/descending
order
SELECT *
FROM <table_name>
ORDER BY <column1><ascending/descending>;
UPDATE
Update values which satisfy condition UPDATE <table_name>
SET <column_name>=<new_value>;
Update all values of a specific column(same
values for a particular column)
UPDATE <table_name>
SET <column_name>=<new_value>
WHERE<condition>;
DELETE
Delete specific rows based on condition DELETE
FROM <table_name>
WHERE<condition>;
Clear all data of a table(delete all rows) DELETE
FROM <table_name>;
Identifiers-
An Identifier is essentially a name of a database_name, table_name, column_name or constraint_name.
Rules-
1. First letter must be alphabet (a-z, A-Z).
2. Second and other letters can be numbers (0-9), alphabet (a-z, A-Z) and _ (underscore).
3. Must not be a keyword.