In last chapter we created table. It has 3 columns:
user_key, user_name and user_password. Let's say we
would like to populate the table with some data.
To add rows into the table we would use clause:
INSERT INTO ...
We have 3 users. All the users have the same
password. So we would use 3 commands to do so:
insert into users (user_name, user_password)
values ('user1','pass');
insert into users (user_name, user_password)
values ('user2','pass');
insert into users (user_name, user_password)
values ('user3','pass');
In some cases we know what rows we want to insert
and we don't want to waste computer and network
resources to run multiple commands. In that case it's
possible to insert all the known rows at once. This
can be achieved by:
insert into users (user_name, user_password) values
('user1','pass'),
('user2','pass'),
('user3','pass')
;
In either case table users now contains 3 rows.
It has to be said that the table users had 3
columns. But we specified only 2 columns for the data
inserting.
The reason is we have user_key specified as
autoincrement and if it's not specified in the insert
clause it does auto populate itself when the column
is ommited while inserting data into the table.
Inserting data is a Data Manipulation Language
(DML). Normally if the database is not in the
autocommit mode we would have to issue COMMIT command
after each DML statement. Previous chapter was given
to data creating. CREATE TABLE is Data Definition
Language. When using DDL statements there is no need
to COMMIT data. It changes the structure of current
database and no COMMIT is needed.
If we would like to add 4th row and provide the
INSERT statement without the columns specification we
would have to explicitly name all the 3 columns like
this:
insert into users values (4,'user4','pass');
In next chapter we will try to query prepared data.
