In a relational
database, data is stored in tables.
An example table would relate Social
Security Number, Name, and Address:
|
EmployeeAddressTable |
| SSN |
FirstName |
LastName |
Address |
City |
State |
| 612687458 |
Joe |
Smith |
83 First Street |
Howard |
Ohio |
| 758420012 |
Mary |
Scott |
842 Vine Ave. |
Losantiville |
Ohio |
| 102254896 |
Sam |
Jones |
33 Elm St. |
Paris |
New York |
| 876512563 |
Sarah |
Ackerman |
440 U.S. 110 |
Upton |
Michigan |
Now, let's say you
want to see the address of each employee.
Use the SELECT statement, like so:
SELECT FirstName,
LastName, Address, City, State
FROM EmployeeAddressTable;
The following is the results of your
query of the database:
| First Name |
Last Name |
Address |
City |
State |
| Joe |
Smith |
83 First Street |
Howard |
Ohio |
| Mary |
Scott |
842 Vine Ave. |
Losantiville |
Ohio |
| Sam |
Jones |
33 Elm St. |
Paris |
New York |
| Sarah |
Ackerman |
440 U.S. 110 |
Upton |
Michigan |
To explain what you
just did, you asked for the all of
data in the EmployeeAddressTable,
and specifically, you asked for the
columns called FirstName, LastName,
Address, City, and State. Note that
column names and table names do not
have spaces...they must be typed as
one word; and that the statement ends
with a semicolon (;). The general
form for a SELECT statement, retrieving
all of the rows in the table
is:
SELECT ColumnName,
ColumnName, ...
FROM TableName;
To get all columns of a table without
typing all column names, use:
SELECT * FROM
TableName;
Each database management
system (DBMS) and database software
has different methods for logging
in to the database and entering SQL
commands; see the local computer "guru"
to help you get onto the system, so
that you can use SQL. |
