MySQL BIT Data Type

Summary: in this tutorial, you will learn about MySQL BIT data type and how to store BIT data in a column of a table.

Introduction to MySQL BIT data type

The BIT data type that allows you to store bit values, which are 0 and 1.

Here’s the syntax for defining BIT type of a column:

column_name BIT(n)Code language: SQL (Structured Query Language) (sql)

The BIT(n) can store up to n-bit values. The n can range from 1 to 64. The default value of n is 1 if you skip it.

So the following syntaxes are equivalent:

column_name BIT(1);Code language: SQL (Structured Query Language) (sql)

and

column_name BIT;Code language: SQL (Structured Query Language) (sql)

BIT literals

To specify a bit value literal, you use b'val' or 0bval notation, which val is a binary value that contains only 0 and 1.

The leading b can be written as B, for example, the following are valid bit literals:

b01
B11Code language: SQL (Structured Query Language) (sql)

However, the leading 0b is case-sensitive. Therefore, you cannot use 0B. For example, the following is an invalid bit literal value:

0B'1000'Code language: SQL (Structured Query Language) (sql)

By default the character set of a bit-value literal is the binary string as follows:

SELECT CHARSET(B'); -- binaryCode language: SQL (Structured Query Language) (sql)

MySQL BIT data type examples

The following statement creates a new table named working_calendars that has the days column is BIT(7):

CREATE TABLE working_calendars(
    year INT,
    week INT,
    days BIT(7),
    PRIMARY KEY(year,week)
);Code language: SQL (Structured Query Language) (sql)

The values in the column days indicate whether the day is a working day or day off i.e., 1: working day and 0: day off.

Suppose that Saturday and Friday of the first week of 2017 are not working days, you can insert a row into the working_calendars table:

INSERT INTO working_calendars(year,week,days)
VALUES(2017,1,B'1111100');Code language: SQL (Structured Query Language) (sql)

The following query retrieves data from the working_calendar table:

SELECT 
    year, week, days
FROM
    working_calendars;Code language: SQL (Structured Query Language) (sql)

Output:

+------+------+------------+
| year | week | days       |
+------+------+------------+
| 2017 |    1 | 0x7C       |
+------+------+------------+
1 row in set (0.00 sec)Code language: JavaScript (javascript)

The output indicates that the bit value in the  days column is converted into an integer. To represent it as bit values, you use the BIN function:

SELECT 
    year, week, bin(days)
FROM
    working_calendars;Code language: SQL (Structured Query Language) (sql)

Output:

+------+------+-----------+
| year | week | bin(days) |
+------+------+-----------+
| 2017 |    1 | 1111100   |
+------+------+-----------+
1 row in set (0.00 sec)Code language: JavaScript (javascript)

If you insert a value into a BIT(n) column that is less than n bits long, MySQL will pad zeros on the left of the bit value.

Suppose the first day of the second week is off, you can insert 01111100 into the  days column. However, the 111100 value will also work because MySQL will pad one zero to the left.

INSERT INTO working_calendars(year,week,days)
VALUES(2017,2,B'111100');Code language: SQL (Structured Query Language) (sql)

To view the data you use the same query as above:

SELECT 
    year, week , bin(days)
FROM
    working_calendars; Code language: SQL (Structured Query Language) (sql)

Output:

+------+------+-----------+
| year | week | bin(days) |
+------+------+-----------+
| 2017 |    1 | 1111100   |
| 2017 |    2 | 111100    |
+------+------+-----------+
2 rows in set (0.00 sec)Code language: JavaScript (javascript)

The output shows that MySQL removed the leading zeros before returning the result. To display it correctly, you can use the LPAD() function:

SELECT 
    year, week, lpad(bin(days),7,'0')
FROM
    working_calendars;Code language: SQL (Structured Query Language) (sql)

Output:

+------+------+-----------------------+
| year | week | lpad(bin(days),7,'0') |
+------+------+-----------------------+
| 2017 |    1 | 1111100               |
| 2017 |    2 | 0111100               |
+------+------+-----------------------+
2 rows in set (0.00 sec)Code language: JavaScript (javascript)

The output shows the expected format.

Summary

• Use MySQL BIT data type to store BIT data in a table.