SQL FROM tables.
The Select FROM statement.
-
Since we can select the data from multiple tables using the FROM,
same column names may exist in several of these tables.
-
To select a specific column from a table of several tables,
we need to prefix the column name with the name of the
table or use an ALIAS (short notation) for the name of the table.
The syntax which are used to specify an alias for a table or view is:
SELECT select_list
FROM [qualifier.]{table_name | view_name} [AS] [alias]
[, [qualifier.]{table_name | view_name} [AS] [alias] ]...
Example for one table:
MySQL, Oracle, SQL server, PostgreSQL:
select o.Order_ID as "Order", o.ISBN_no as "ISBN",
o.Item_qty "Quantity", o.price "Price", o.Item_qty*price "Product"
from order_BOOKS o
where o.order_ID=70001;
The result should be:
Order
ISBN
Quantity
Price
Product
70001
0201703092
2
39
78
70001
0764557599
1
42
42
70001
1861002025
5
38
190
70001
1861006314
2
29
58
The syntax which are used to specify an alias for a table or view is:
SELECT select_list
FROM [qualifier.]{table_name | view_name} [AS] [alias]
[, [qualifier.]{table_name | view_name} [AS] [alias] ]...
Example for one table:
MySQL, Oracle, SQL server, PostgreSQL:
select o.Order_ID as "Order", o.ISBN_no as "ISBN",
o.Item_qty "Quantity", o.price "Price", o.Item_qty*price "Product"
from order_BOOKS o
where o.order_ID=70001;
The result should be:
Order | ISBN | Quantity | Price | Product |
---|---|---|---|---|
70001 | 0201703092 | 2 | 39 | 78 |
70001 | 0764557599 | 1 | 42 | 42 |
70001 | 1861002025 | 5 | 38 | 190 |
70001 | 1861006314 | 2 | 29 | 58 |
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