INSERT INTO tbl_01(id, name) VALUES (1, ‘One’)

INSERT INTO tbl_01(id, name) VALUES(2, ‘Two’)

But also

INSERT INT tbl_01(id, name) VALUES

(1, ‘One’), (2, ‘Two’)

In practice it is very useful.

The syntax for creating a sequence is :

CREATE SEQUENCE sequence_name
MINVALUE value
MAXVALUE value
START WITH value
INCREMENT BY value
CACHE value;

If you omit the MAXVALUE, it will default to

MAXVALUE 999999999999999999999999999

To retrieve the next value from the sequence, nextval is to be used :

sequence_name.nextval

The nextval statement needs to be used in an SQL statement, for instance :

INSERT INTO tbl_name(tbl_id, tbl_col_name)
VALUES(sequence_name.nextval, ‘Name’);

The CACHE option specifies how many values would be stored in memory for faster access. It sounds good, but if for some reason a system failure occurs, all cached sequence values would be “lost” – when the system is be back up, the sequence will use the next value starting from MINVALUE + CACHE. NOCACHE sacrifices some performance, but you won’t get a “gap” in the values.

Oracle DOES NOT implement any column with autoincrement property. In turn, MySQL does not support sequences. MySQL uses autoincrement,applied to the primary key during table creation :

create table tbl_01 (id int primary key auto_increment, name varchar(100));

The value for the primary key will be assigned automatically, if during an insert there is no value manually assigned to the id column.

Note that the “sequence” will start from the highest value. If we manually insert a record with a number for the id higher than the maximum id in that table, the next insert with no value for the id will automatically assign that max value incremented.

For example suppose you have the following data in the table:

id name

1 One

2 Two

3 Three

You do an insert like this :

INSERT INTO tbl_01(id, name) VALUES (10, ‘Ten’);

You will end up with the following table :

id name

1 One

2 Two

3 Three

10 Ten

When you execute the following SQL:

INSERT INTO TABLE tbl_01(name) VALUES (’Next’);

You will end up with :

id name

1 One

2 Two

3 Three

10 Ten

11 Next

You can insert record with a value for the id lower than the MAX(id) and that will not affect the next autoincrement value. It just has to follow the normal rules for the primary key (no duplicates).

Also if all the records are deleted from the table, the autoincrement is not affected (it will continue to assign the incremented MAX(id) based on the values that were previously in the table). In order to “reset the sequence” a the table must be truncated :

truncate table tbl_01

Now the first automatically generated value for the id will be 1. You can achieve the same by :

ALTER TABLE tbl_01 auto_increment=value

Compared to Oracle, MySQL is pretty straightforward, but does have its [big] limitations: it cannot be used across multiple tables and you cannot set different increment values.

SELECT * FROM tbl_01 WHERE name = ‘paul’

In Oracle this query would return only the rows containing ‘paul’ in the column name, because Oracle is case sensitive.

MySQL is not, so the same query would return rows containing ‘Paul’, ‘paul’, ‘pAul’, etc. In order to force MySQL to check for the exact case, the keyword binary has to be used :

SELECT * FROM tbl_01 WHERE binary name = “paul”

There is also an alternative to this – making a column case sensitive on table creation:

CREATE TABLE tbl_01 (name varchar(100) binary);

Now the select on name cares for the way the name is written.