I can not understand why this option.
The signed TINYINT data type can store integer values between -128 and 127.
mysql> create table b (i tinyint(1));
mysql> insert into b values (42);
mysql> select * from b;
+------+
| i |
+------+
| 42 |
+------+
Data-wise, tinyint(1), tinyint(2), tinyint(3) etc. are all exactly the same. They are all in the range -128 to 127 for SIGNED or 0-255 for UNSIGNED. As other answers noted the number in parenthesis is merely a display width hint.
You might want to note, though, that application=wise things may look different. Here, tinyint(1) can take a special meaning. For example, the Connector/J (Java connector) treats tinyint(1) as a boolean value, and instead of returning a numerical result to the application, it converts values to true and false. this can be changed via the tinyInt1isBit=false connection parameter.
A tinyint(1) can hold numbers in the range -128 to 127, due to the datatype being 8 bits (1 byte) - obviously an unsigned tinyint can hold values 0-255.
It will silently truncate out of range values:
mysql> create table a
-> (
-> ttt tinyint(1)
-> );
Query OK, 0 rows affected (0.01 sec)
mysql> insert into a values ( 127 );
Query OK, 1 row affected (0.00 sec)
mysql> insert into a values ( -128 );
Query OK, 1 row affected (0.00 sec)
mysql> insert into a values ( 128 );
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> insert into a values ( -129 );
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> select * from a;
+------+
| ttt |
+------+
| 127 |
| -128 |
| 127 |
| -128 |
+------+
4 rows in set (0.00 sec)
mysql>
... unless you change the sql_mode or change the server config:
mysql> set sql_mode=STRICT_ALL_TABLES;
Query OK, 0 rows affected (0.00 sec)
mysql> insert into a values ( -129 );
ERROR 1264 (22003): Out of range value for column 'ttt' at row 1
mysql>
The value used in the DDL for the datatype (eg: tinyint(1)) is, as you suspected, the display width. However, it is optional and clients don't have to use it. The standard MySQL client doesn't use it, for example.
https://dev.mysql.com/doc/refman/5.1/en/integer-types.html
https://dev.mysql.com/doc/refman/5.0/en/numeric-type-overview.html
MySql: Tinyint (2) vs tinyint(1) - what is the difference?
The lenght parameter for numeric data types only affect the display width, but not the value that can be stored.
TINYINT -128 to 127 (or 0-255 unsigned)
SMALLINT -32768 to 32767 (or 0-65535 unsigned)
MEDIUMINT -8388608 to 8388607 (or 0-16777215 unsigned)
INT -2147483648 to 2147483647 (or 0-4294967295 unsigned)
BIGINT -9223372036854775808 to 9223372036854775807 (or 0-18446744073709551615 unsigned)
Related
This does not make sense to me. Can anyone explain it? I think the column values should be different, so
select * from a1 where f1 = f2;
should find no rows. But...
mysql> create table a1 (f1 varchar(63), f2 varchar(63));
Query OK, 0 rows affected (0.00 sec)
mysql> show create table a1 \G
*************************** 1. row ***************************
Table: a1
Create Table: CREATE TABLE `a1` (
`f1` varchar(63) DEFAULT NULL,
`f2` varchar(63) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.00 sec)
mysql>
mysql> insert into a1 values ('EFBBBFD187D0B5D0BBD0BED0B2D0B5D0BA', 'EFBBBFD187D0B5D0BBD0BED0B2D0B5CC81D0BA');
Query OK, 1 row affected (0.02 sec)
mysql> update a1 set f1 = unhex(f1);
Query OK, 1 row affected (0.02 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update a1 set f2 = unhex(f2);
Query OK, 1 row affected (0.02 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from a1;
+-------------------+---------------------+
| f1 | f2 |
+-------------------+---------------------+
| человек | челове́к |
+-------------------+---------------------+
1 row in set (0.00 sec)
mysql>
mysql>
mysql> select * from a1 where f1 = f2;
+-------------------+---------------------+
| f1 | f2 |
+-------------------+---------------------+
| человек | челове́к |
+-------------------+---------------------+
1 row in set (0.00 sec)
mysql> select * from a1 where hex(f1) = hex(f2);
Empty set (0.00 sec)
mysql>
The 3 bytes on the beginning, EFBBBF, is "BOM", which indicates that the text is UTF-8-encoded.
The rest look like Cyrillic челове́к, except for the "CC81 -- NSM COMBINING ACUTE ACCENT"
Some collations, including utf8mb4_0900_ai_ci, handle "combining accents", some do not. The "ai" means "accent insensitive".
I would understand this equivalence for a "latin" e. I don't know the rules for a CYRILLIC SMALL LETTER IE, which looks the same е, but is encoded differently.
You might want COLLATE utf8mb4_0900_as_ci, which is "accent sensitive and case insensitive".
Character equivalence is defined by the collation used by the columns in question. A collation defines every pair of characters as equal, less than, or greater than, and this is used for comparisons and for sorting.
Your table uses utf8mb4_0900_ai_ci as the default collation, and this applies to all the columns, since they do not define a collation to override the table's default.
It's pretty common for collations to treat accented characters as equal to their unaccented versions.
If you want to choose a different collation, you may.
I have a field id defined as below. It's varbinary(16) in database, when i am inserting a new record through JPA, i got "com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'ID' at row 1". What am I doing wrong?
#Id
#Column(name="ID")
private UUID id;
A UUID is a 128-bit number represented by a utf8 string of five hexadecimal numbers separated by hyphen( '-' ). Char length of the string returned by UUID() is '36'.
Hence column definition with '16' length is not sufficient. And when defined so, you will receive the said error.
mysql> create table tbl_so_q24028471_vb( v varbinary(16) );
Query OK, 0 rows affected (0.42 sec)
mysql> desc tbl_so_q24028471_vb;
+-------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------------+------+-----+---------+-------+
| v | varbinary(16) | YES | | NULL | |
+-------+---------------+------+-----+---------+-------+
1 row in set (0.17 sec)
mysql> insert into tbl_so_q24028471_vb values( uuid() );
ERROR 1406 (22001): Data too long for column 'v' at row 1
Change the column definition to accommodate more length and use.
mysql> alter table tbl_so_q24028471_vb modify column v varbinary(36);
Query OK, 0 rows affected (0.86 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> insert into tbl_so_q24028471_vb values( uuid() );
Query OK, 1 row affected (0.08 sec)
mysql> select * from tbl_so_q24028471_vb;
+--------------------------------------+
| v |
+--------------------------------------+
| 630d3270-ebba-11e3-bd03-bc8556a95cc2 |
+--------------------------------------+
Your trying to store a 36 character string in a 16 byte space. That's not going to work.
You need get at the bits behind the UUID, which will fit in a binary(16). Since you're using Java, you can do something like:
ByteBuffer bb = ByteBuffer.wrap(new byte[16]);
bb.putLong(uuid.getMostSignificantBits());
bb.putLong(uuid.getLeastSignificantBits());
return bb.array();
and then insert the resulting byte array into the DB.
Is their an int field in mysql where negative numbers are not allowed? or more specifically if a negative number is inserted into the field it will insert a zero. I ask this because we have a scoring system and we don't allow people to have negative scores. So if their score does reach bellow zero, it will just insert a zero instead. I'm trying to do this without having to query the user's score to check if it will fall bellow zero.
In addition to the DDL change (INT UNSIGNED) that others have recommended, I'd also change your application logic. You say:
I'm trying to do this without having to query the user's score to check if it will fall bellow zero.
You don't have to explicitly check in a separate query:
UPDATE your_table
SET score = GREATEST(score + ?, 0) -- This '?' is the adjustment to the score
WHERE user_id = ?
Now your application cannot UPDATE score to fall below zero, nor will it generate errors or warnings depending on the SQL mode.
Yes. You can create an int field and mark it as UNSIGNED.
From MySQL 5.0 Reference Manual:
INT[(M)] [UNSIGNED] [ZEROFILL]
A normal-size integer. The signed range is -2147483648 to 2147483647.
The unsigned range is 0 to 4294967295.
MySQL has an UNSIGNED qualifier for integer types.
Negative values will be clamped to zero, but will generate a warning:
mysql> create table test ( id int(5) unsigned not null );
Query OK, 0 rows affected (0.05 sec)
mysql> insert into test values (-1), (5), (10);
Query OK, 3 rows affected, 1 warning (0.01 sec)
Records: 3 Duplicates: 0 Warnings: 1
mysql> select * from test;
+----+
| id |
+----+
| 0 |
| 5 |
| 10 |
+----+
3 rows in set (0.01 sec)
If you are running in strict sql mode this would throw an error and an insert/update would fail.
I usally create a user-defined function for this sort of thing. (In this case a very trivial "if (expr1, expr2, expr3)" will do the trick
I just want to know what is the benefit/usage of defining ZEROFILL for INT DataType in MySQL?
`id` INT UNSIGNED ZEROFILL NOT NULL
When you select a column with type ZEROFILL it pads the displayed value of the field with zeros up to the display width specified in the column definition. Values longer than the display width are not truncated. Note that usage of ZEROFILL also implies UNSIGNED.
Using ZEROFILL and a display width has no effect on how the data is stored. It affects only how it is displayed.
Here is some example SQL that demonstrates the use of ZEROFILL:
CREATE TABLE yourtable (x INT(8) ZEROFILL NOT NULL, y INT(8) NOT NULL);
INSERT INTO yourtable (x,y) VALUES
(1, 1),
(12, 12),
(123, 123),
(123456789, 123456789);
SELECT x, y FROM yourtable;
Result:
x y
00000001 1
00000012 12
00000123 123
123456789 123456789
One example in order to understand, where the usage of ZEROFILL might be interesting:
In Germany, we have 5 digit zipcodes. However, those Codes may start with a Zero, so 80337 is a valid zipcode for munic, 01067 is a zipcode of Berlin.
As you see, any German citizen expects the zipcodes to be displayed as a 5 digit code, so 1067 looks strange.
In order to store those data, you could use a VARCHAR(5) or INT(5) ZEROFILL whereas the zerofilled integer has two big advantages:
Lot lesser storage space on hard disk
If you insert 1067, you still get 01067 back
Maybe this example helps understanding the use of ZEROFILL.
It's a feature for disturbed personalities who like square boxes.
You insert
1
23
123
but when you select, it pads the values
000001
000023
000123
It helps in correct sorting in the case that you will need to concatenate this "integer" with something else (another number or text) which will require to be sorted as a "text" then.
for example,
if you will need to use the integer field numbers (let's say 5) concatenated as A-005 or 10/0005
I know I'm late to the party but I find the zerofill is helpful for boolean representations of TINYINT(1). Null doesn't always mean False, sometimes you don't want it to. By zerofilling a tinyint, you're effectively converting those values to INT and removing any confusion ur application may have upon interaction. Your application can then treat those values in a manner similar to the primitive datatype True = Not(0)
mysql> CREATE TABLE tin3(id int PRIMARY KEY,val TINYINT(10) ZEROFILL);
Query OK, 0 rows affected (0.04 sec)
mysql> INSERT INTO tin3 VALUES(1,12),(2,7),(4,101);
Query OK, 3 rows affected (0.02 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM tin3;
+----+------------+
| id | val |
+----+------------+
| 1 | 0000000012 |
| 2 | 0000000007 |
| 4 | 0000000101 |
+----+------------+
3 rows in set (0.00 sec)
mysql>
mysql> SELECT LENGTH(val) FROM tin3 WHERE id=2;
+-------------+
| LENGTH(val) |
+-------------+
| 10 |
+-------------+
1 row in set (0.01 sec)
mysql> SELECT val+1 FROM tin3 WHERE id=2;
+-------+
| val+1 |
+-------+
| 8 |
+-------+
1 row in set (0.00 sec)
ZEROFILL
This essentially means that if the integer value 23 is inserted into an INT column with the width of 8 then the rest of the available position will be automatically padded with zeros.
Hence
23
becomes:
00000023
When used in conjunction with the
optional (nonstandard) attribute
ZEROFILL, the default padding of
spaces is replaced with zeros. For
example, for a column declared as
INT(4) ZEROFILL, a value of 5 is
retrieved as 0005.
http://dev.mysql.com/doc/refman/5.0/en/numeric-types.html
If you specify ZEROFILL for a numeric column, MySQL automatically adds the UNSIGNED attribute to the column.
Numeric data types that permit the UNSIGNED attribute also permit SIGNED. However, these data types are signed by default, so the SIGNED attribute has no effect.
Above description is taken from MYSQL official website.
I've learned this along the way but can't figure out where I read it or heard it, as there is nothing I have found online supporting it, but I remember that when upgrading from mysql4.x to mysql5.x, one of the required changes was that the auto-increment field for inserts had to change from '' to NULL if it was included.
I know its not required to have in the insert anyway, but just for point of interest...
Mysql 4.x would allow:
INSERT INTO TABLE (table_id, name, location) VALUES ('', 'john', 'NY');
But mysql 5.x had to have:
INSERT INTO TABLE (table_id, name, location) VALUES (NULL, 'john', 'NY');
I can't find any information on mysql's site to support this, but I know for a fact it throws an error in mysql 5.x and know it worked with '' in 4.x, but where is this documented?
Both the 4.1 and 5.0 docs state that 0 or NULL is required:
No value was specified for the
AUTO_INCREMENT column, so MySQL
assigned sequence numbers
automatically. You can also explicitly
assign NULL or 0 to the column to
generate sequence numbers.
It does not matter, mysql internally still convert to integer
mysql> CREATE TABLE some_test ( id int(10) unsigned NOT NULL auto_increment, primary key(id));
Query OK, 0 rows affected (0.00 sec)
mysql> insert into some_test values ('');
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> show warnings;
+---------+------+------------------------------------------------------+
| Level | Code | Message |
+---------+------+------------------------------------------------------+
| Warning | 1264 | Out of range value adjusted for column 'id' at row 1 |
+---------+------+------------------------------------------------------+
1 row in set (0.00 sec)
mysql> select * from some_test;
+----+
| id |
+----+
| 1 |
+----+
1 row in set (0.00 sec)
However, I will suggest use 0 to avoid this warning