Oracle SQL in 10 Minutes - Asim Abbasi
CH1: SQL Basics | CH2: SQL Operators | CH3: SQL Built-in Functions | CH4: SQL Joins | CH5: UPDATE, INSERT & DELETE Statements | CH6: CREATE, ALTER & DROP Statements | CH7: Constraints | CH8: Linking Tables vs Joining Tables | CH9: SQL Statements for Other Database Objects | CH10: SQL Statements for Database Security
Chapter 6: CREATE, ALTER & DROP Statement
CREATE & DROP Table Statements:
Figure 12: CREATE/DROP TABLE Statement
________________________________________
Before explaining how to create table I would like to give you slight
explanation about the word “Schema”, what it is? And what it means in
Oracle Jargon. Schema is basically a Latin word and it means, a
diagrammatic representation; an outline or model. Schema can be
visualized by looking at the organization chart of a company e.g., the
one shown below.
Figure 13: Organizational Chart. Showing Chief’s
Schema
________________________________________
Each user we create in Oracle database is a “Schema”.
All the objects (tables, Views, Sequences etc.) created by that user
fall under his schema. Oracle DBA (Database Administrator) is the owner
of all the schemas and the objects under each. He is just like the
“Chief” in the Figure 13.
To create table first you have to decide which schema you want this
table to be in. Then log into Oracle system (usually SQL*Plus) using
that schema’s (or User’s) credentials i.e. username/password. Upon
successful login, execute the CREATE TABLE command to create required
table under that schema.
If you look in the Figure 12, especially on the syntax of CREATE TABLE
statement, there is something mentioned called the “data type” besides
table name which will be name of the table that you want to create and
the columns names which will be the names of the columns that you want
to be in the table. While creating table you also have to tell Oracle
what type of data goes in which column or in other words data type of
each column e.g., if you tell oracle that I want to store date type of
information in first column and text type of information in second
column then while inserting data into this table using the INSERT
statement you cannot insert number or currency information in first
column. If you do so, you will get “type miss-match” like error. Now
lets see what different types of “Data Types” are available in Oracle so
we can utilize them in the data type assignment of each column within a
table in the CREATE TABLE statement.
Chapter 5: CREATE, ALTER & DROP Statement
CH1: SQL Basics | CH2:
SQL Operators |
CH3: SQL Built-in Functions | CH4:
SQL Joins | CH5:
UPDATE, INSERT & DELETE Statements |
CH6: CREATE, ALTER & DROP Statements | CH7:
Constraints | CH8:
Linking Tables vs Joining Tables | CH9:
SQL
Statements for Other Database Objects | CH10:
SQL Statements for
Database Security Share with others: