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
Related
This is my column
As It's length is specified (smallint(4)), but it does not constrain the range of values
, so how can I constrain that only 4 digit values can be entered in this column
"In query" validation can be done like this:
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table (year INT NOT NULL);
INSERT INTO my_table SELECT 2016 FROM (SELECT 1) n WHERE 2016 BETWEEN 0 AND 9999;
Query OK, 1 row affected (0.00 sec)
SELECT * FROM my_table;
+------+
| year |
+------+
| 2016 |
+------+
INSERT INTO my_table SELECT 20161 FROM (SELECT 1) n WHERE 20161 BETWEEN 0 AND 9999;
Query OK, 0 rows affected (0.00 sec)
SELECT * FROM my_table;
+------+
| year |
+------+
| 2016 |
+------+
From MySQL manual:
MySQL supports an extension for optionally specifying the display width of integer data types in parentheses following the base keyword for the type. For example, INT(4) specifies an INT with a display width of four digits.
The display width does not constrain the range of values that can be stored in the column. Nor does it prevent values wider than the column display width from being displayed correctly. For example, a column specified as SMALLINT(3) has the usual SMALLINT range of -32768 to 32767, and values outside the range permitted by three digits are displayed in full using more than three digits.
So, you cannot limit only 4 digit values in mysql this way. And MySQL does not supports custom CHECK constraints. But you can create trigger like this and check value inside. Note, that SIGNAL works since MySQL 5.5.
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)
Recently MySQL 5.1.49 (OSX) started inserting the same value '2147483647' for ALL integer fields named id and set as primary key. This is happening for all databases and all tables. Here's the a quick example:
mysql> INSERT INTO packages(id,name,rate) VALUES ('37364428662',"Testing","300");
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> SELECT * FROM packages;
+------------+---------+------+
| id | name | rate |
+------------+---------+------+
| 2147483647 | Testing | 300 |
+------------+---------+------+
1 row in set (0.00 sec)
mysql>
I'm attempting to re-install MYSQL as nothing else seems to be working : / I'll post any solutions I manage but meanwhile any help is always appreciated!
It's probably because your id field is a 32 bit integer and the value 37364428662 will require more than 32 bits to store. Try changing the type of id to an unsigned int, or some larger integer type.
It appears when you try to enter 37364428662 it's defaulting to the largest possible value for an int 32 (2147483647).
You want to insert a value for an id 37364428662 which is larger then the maximum allowed size of your integer field (2147483647).
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