<span style='</span></div><div align="center">بسم الله الرحمن الرحيم
Displaying Table Structure:
In SQL*Plus, you can display the structure of a table using the DESCRIBE command. The result of the command is to see the column names, Datatypes, and whether a column must contain data.
*********************
DESC[RIBE] tablename
********************
Where: tablename is the name of any existing table, view, or synonym accessible to the user.
Example:
Display information about the structure of the S_DEPT table.
#####################
SQL> DESCRIBE s_dept
#####################
NAME NULL? Type
--------- --------- -------
ID NOT NULL NUMBER (7)
NAME NOT NULL VARCHAR2 (25)
REGION_ID NUMER (7)
###########################
Where: Null? Indicates that a column must contain data.
Type displays the datatype for a column.
&&&&&&&&&&&&&&&&&&&&&&&&
Datatype Description
=======================================
NUMBER (p,s)```` Description
***************************
VARCHAR2(s) Number value having a maximum number of digits p , and the number of digits to the right of the decimal point s .
**********************************
DATE Variable length character value of maximum size s .
*************************************
CHAR(s) Fixed length character value of size s.
================================
The Basic Query Block:
A SELECT statement retrieves information from the database, implementing all algebraic operators .
Syntax
¬+++++++++++++++++++++++
SELECT (DISTINCT) {* , column [alias] , …. }
FROM table ;
+++++++++++++++++++++++
Where : SELECT is a list of at least one column .
DISTINCT suppresses duplicates .
* select all columns .
column selects the named column .
alias gives selected columns a different heading
FROM table specifies the table containing the columns.
Selecting All Columns and Rows
The asterisk (*) selects all columns from the table .
Example
List all columns and all rows from the S_DEPT table .
&&&&&&&&&&&&&&&&&&&&&&
SQL> SELECT *
2 FROM s_dept;
##################################
ID NAME REGION_ID
---- --------- ------------------
10 Finance 1
31 Sales 1
32 Sales 2
33 Sales 3
34 Sales 4
35 Sales 5
41 Operations 1
42 Operations 2
43 Operations 3
44 Operations 4
45 Operations 5
50 Administration 1
12 Rows selected .
###################################################
Selecting Specific Columns:
You restrict the query to display only certain columns by specifying the column names , separated by commas , in the SELECT clause .
Example:
Display all department numbers, employee last names, and manager numbers in the S_EMP table .
######################
SQL> SELECT dept_id, last_name, manager_id
2 FROM s_emp;
**********************
DEPT_ID LAST_NAME MANAGER_ID
------------- ------------------- ---------------------
50 Velasquez
41 Ngao 1
31 Nagayama 1
10 Quick-to-see 1
50 Ropeburn 1
41 Urguhart 2
42 Menchu 2
43 Biri 2
44 Catchpole 2
…
25 rows selected
==========================================
المعذرة بعض الأرقام بالعربي وبعض الفواصل مقلوبة مادري ليش
(( والدروس القادمة افضل ان شاء الله))
وشكر الأخوان الأفاضل القائمين على هذا النتدى
(( محبكم ابوفهد abu_fahad2004@hotmail.com ))
