For integer data types, 对于整数数据类型，M indicates the maximum display width. M表示最大显示宽度。The maximum display width is 255. 最大显示宽度为255。Display width is unrelated to the range of values a type can store, as described in Section 11.1.6, “Numeric Type Attributes”.显示宽度与类型可以存储的值范围无关，如第11.1.6节，“数字类型属性”所述。
For floating-point and fixed-point data types, 对于浮点和定点数据类型，M is the total number of digits that can be stored.M是可以存储的总位数。
As of MySQL 8.0.17, the display width attribute is deprecated for integer data types; you should expect support for it to be removed in a future version of MySQL.从MySQL8.0.17开始，整数数据类型不再使用display width属性；您应该期望在MySQL的未来版本中删除对它的支持。
If you specify 如果为数字列指定ZEROFILL for a numeric column, MySQL automatically adds the UNSIGNED attribute to the column.ZEROFILL，MySQL会自动向该列添加UNSIGNED属性。
As of MySQL 8.0.17, the 从MySQL8.0.17开始，数字数据类型不推荐使用ZEROFILL attribute is deprecated for numeric data types; you should expect support for it to be removed in a future version of MySQL. ZEROFILL属性；您应该期望在MySQL的未来版本中删除对它的支持。Consider using an alternative means of producing the effect of this attribute. 考虑使用另一种方法来产生此属性的效果。For example, applications could use the 例如，应用程序可以使用LPAD() function to zero-pad numbers up to the desired width, or they could store the formatted numbers in CHAR columns.LPAD()函数将填充数字归零到所需的宽度，也可以将格式化的数字存储在CHAR列中。
Numeric data types that permit the 允许UNSIGNED attribute also permit SIGNED. UNSIGNED属性的数字数据类型也允许SIGNED属性。However, these data types are signed by default, so the 但是，这些数据类型在默认情况下是有符号的，因此SIGNED attribute has no effect.SIGNED属性无效。
As of MySQL 8.0.17, the 从MySQL 8.0.17开始，对于UNSIGNED attribute is deprecated for columns of type FLOAT, DOUBLE, and DECIMAL (and any synonyms); you should expect support for it to be removed in a future version of MySQL. FLOAT、DOUBLE和DECIMAL（以及任何同义词）类型的列，UNSIGNED属性就不再使用了；您应该期望在MySQL的未来版本中删除对它的支持。Consider using a simple 考虑对此类列使用简单的CHECK constraint instead for such columns.CHECK约束。
SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE.SERIAL是BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE的别名。
SERIAL DEFAULT VALUE in the definition of an integer column is an alias for NOT NULL AUTO_INCREMENT UNIQUE.SERIAL DEFAULT VALUE在整型数列的定义中是NOT NULL AUTO_INCREMENT UNIQUE的别名。
When you use subtraction between integer values where one is of type 如果在整型值之间使用减法，其中一个值的类型为UNSIGNED, the result is unsigned unless the NO_UNSIGNED_SUBTRACTION SQL mode is enabled. UNSIGNED，则结果为无符号的，除非启用了NO_UNSIGNED_SUBTRACTION SQL模式。See Section 12.11, “Cast Functions and Operators”.请参见第12.11节，“Cast函数和运算符”。
A bit-value type. 位值类型。M indicates the number of bits per value, from 1 to 64. M表示每个值的位数，从1到64。The default is 1 if 如果省略M is omitted.M，则默认值为1。
TINYINT[(M)] [UNSIGNED] [ZEROFILL]
A very small integer. 一个非常小的整数。The signed range is 有符号范围是-128 to 127. -128到127。The unsigned range is 无符号范围是0 to 255.0到255。
These types are synonyms for 这些类型是TINYINT(1). TINYINT(1)的同义词。A value of zero is considered false. 零值被认为是false。Nonzero values are considered true:非零值被认为是true：
mysql>SELECT IF(0, 'true', 'false');+------------------------+ | IF(0, 'true', 'false') | +------------------------+ | false | +------------------------+ mysql>SELECT IF(1, 'true', 'false');+------------------------+ | IF(1, 'true', 'false') | +------------------------+ | true | +------------------------+ mysql>SELECT IF(2, 'true', 'false');+------------------------+ | IF(2, 'true', 'false') | +------------------------+ | true | +------------------------+
However, the values 但是，值TRUE and FALSE are merely aliases for 1 and 0, respectively, as shown here:TRUE和FALSE分别只是1和0的别名，如下所示：
mysql>SELECT IF(0 = FALSE, 'true', 'false');+--------------------------------+ | IF(0 = FALSE, 'true', 'false') | +--------------------------------+ | true | +--------------------------------+ mysql>SELECT IF(1 = TRUE, 'true', 'false');+-------------------------------+ | IF(1 = TRUE, 'true', 'false') | +-------------------------------+ | true | +-------------------------------+ mysql>SELECT IF(2 = TRUE, 'true', 'false');+-------------------------------+ | IF(2 = TRUE, 'true', 'false') | +-------------------------------+ | false | +-------------------------------+ mysql>SELECT IF(2 = FALSE, 'true', 'false');+--------------------------------+ | IF(2 = FALSE, 'true', 'false') | +--------------------------------+ | false | +--------------------------------+
The last two statements display the results shown because 最后两个语句显示所显示的结果，因为2 is equal to neither 1 nor 0.2既不等于1也不等于0。
SMALLINT[(M)] [UNSIGNED] [ZEROFILL]
A small integer. 一个小整数。The signed range is 带符号范围是-32768 to 32767. -32768到32767。The unsigned range is 无符号范围是0 to 65535.0到65535。
MEDIUMINT[(M)] [UNSIGNED] [ZEROFILL]
A medium-sized integer. 中等大小的整数。The signed range is 带符号范围是-8388608 to 8388607. -8388608到8388607。The unsigned range is 无符号范围是0 to 16777215.0到16777215。
INT[(M)] [UNSIGNED] [ZEROFILL]
A normal-size integer. 正常大小的整数。The signed range is 带符号的范围是-2147483648 to 2147483647. -2147483648到2147483647。The unsigned range is 无符号范围是0 to 4294967295.0到4294967295。
INTEGER[(M)] [UNSIGNED] [ZEROFILL]
This type is a synonym for 此类型是INT.INT的同义词。
BIGINT[(M)] [UNSIGNED] [ZEROFILL]
A large integer. 一个大整数。The signed range is 带符号的范围是-9223372036854775808 to 9223372036854775807. -9223372036854775808到9223372036854775807。The unsigned range is 无符号范围是0 to 18446744073709551615.0到18446744073709551615。
SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE.SERIAL是BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE的别名。
Some things you should be aware of with respect to 关于BIGINT columns:BIGINT列，您应该注意以下几点：
All arithmetic is done using signed 所有的算术都是使用有符号的BIGINT or DOUBLE values, so you should not use unsigned big integers larger than 9223372036854775807 (63 bits) except with bit functions! BIGINT或DOUBLE值来完成的，所以除了位函数外，不应该使用大于9223372036854775807（63位）的无符号大整数！If you do that, some of the last digits in the result may be wrong because of rounding errors when converting a 如果这样做，结果中的一些最后的数字可能是错误的，因为在将BIGINT value to a DOUBLE.BIGINT值转换为DOUBLE时存在舍入错误。
MySQL can handle MySQL可以在以下情况下处理BIGINT in the following cases:BIGINT：
When using integers to store large unsigned values in a 在BIGINT column.BIGINT列中使用整数存储大的无符号值时。
In 在MIN( or col_name)MAX(, where col_name)col_name refers to a BIGINT column.MIN(col_name)或MAX(col_name)中，col_name表示BIGINT列。
When using operators (当使用运算符（+, -, *, and so on) where both operands are integers.+、-、*等）时，其中两个操作数都是整数。
You can always store an exact integer value in a 通过使用字符串存储整数值，可以始终将整数值存储在BIGINT column by storing it using a string. BIGINT列中。In this case, MySQL performs a string-to-number conversion that involves no intermediate double-precision representation.在本例中，MySQL执行字符串到数字的转换，不涉及中间的双精度表示。
The 当两个操作数都是整数值时，-, +, and * operators use BIGINT arithmetic when both operands are integer values. -、+和*运算符使用BIGINT算术。This means that if you multiply two big integers (or results from functions that return integers), you may get unexpected results when the result is larger than 这意味着，如果将两个大整数（或返回整数的函数的结果）相乘，当结果大于9223372036854775807.9223372036854775807时，可能会得到意外的结果。
DECIMAL[(M[,D])] [UNSIGNED] [ZEROFILL]
A packed “exact” fixed-point number. 一个压缩的“精确”定点数。M is the total number of digits (the precision) and D is the number of digits after the decimal point (the scale). M是总位数（精度），D是小数点后的位数（刻度）。The decimal point and (for negative numbers) the 小数点和（对于负数）- sign are not counted in M. -符号未计入M。If 如果D is 0, values have no decimal point or fractional part. D为0，则值没有小数点或小数部分。The maximum number of digits (M) for DECIMAL is 65. DECIMAL的最大位数（M）为65。The maximum number of supported decimals (支持的最大小数位数（D) is 30. D）为30。If 如果省略D is omitted, the default is 0. D，则默认值为0。If 如果省略M is omitted, the default is 10. M，则默认值为10。(There is also a limit on how long the text of （DECIMAL literals can be; see Section 12.25.3, “Expression Handling”.)DECIMAL字面量的文本长度也有限制；请参见第12.25.3节，“表达式处理”。）
UNSIGNED, if specified, disallows negative values. UNSIGNED，则不允许负值。As of MySQL 8.0.17, the 从MySQL 8.0.17开始，对于UNSIGNED attribute is deprecated for columns of type DECIMAL (and any synonyms); you should expect support for it to be removed in a future version of MySQL. DECIMAL类型的列（以及任何同义词）不推荐使用UNSIGNED属性；您应该期望在MySQL的未来版本中删除对它的支持。Consider using a simple 考虑对此类列使用简单的CHECK constraint instead for such columns.CHECK约束。
All basic calculations (所有带+, -, *, /) with DECIMAL columns are done with a precision of 65 digits.DECIMAL列的基本计算（+、-、*、/）的精度为65位。
DEC[(, M[,D])] [UNSIGNED] [ZEROFILL]NUMERIC[(, M[,D])] [UNSIGNED] [ZEROFILL]FIXED[(M[,D])] [UNSIGNED] [ZEROFILL]
These types are synonyms for 这些类型是DECIMAL. DECIMAL的同义词。The FIXED synonym is available for compatibility with other database systems.FIXED同义词可用于与其他数据库系统兼容。
FLOAT[(M,D)] [UNSIGNED] [ZEROFILL]
A small (single-precision) floating-point number. 一个小的（单精度）浮点数。Permissible values are 允许值为-3.402823466E+38 to -1.175494351E-38, 0, and 1.175494351E-38 to 3.402823466E+38. -3.4028234666E+38至-1.175494351E-38、0和1.175494351E-38至3.4028234666E+38。These are the theoretical limits, based on the IEEE standard. 这些是基于IEEE标准的理论极限。The actual range might be slightly smaller depending on your hardware or operating system.根据硬件或操作系统的不同，实际范围可能会稍微小一些。
M is the total number of digits and D is the number of digits following the decimal point. M是总位数，D是小数点后的位数。If 如果省略M and D are omitted, values are stored to the limits permitted by the hardware. M和D，则将值存储到硬件允许的限制范围内。A single-precision floating-point number is accurate to approximately 7 decimal places.单精度浮点数精确到大约7位小数。
FLOAT(M,D) is a nonstandard MySQL extension. 是一个非标准的MySQL扩展。As of MySQL 8.0.17, this syntax is deprecated, and you should expect support for it to be removed in a future version of MySQL.从MySQL8.0.17开始，这种语法就不受欢迎了，您应该希望在将来的MySQL版本中删除对它的支持。
UNSIGNED, if specified, disallows negative values. UNSIGNED，则不允许负值。As of MySQL 8.0.17, the 从MySQL 8.0.17开始，UNSIGNED attribute is deprecated for columns of type FLOAT (and any synonyms) and you should expect support for it to be removed in a future version of MySQL. UNSIGNED属性对于FLOAT类型的列（以及任何同义词）都是不推荐的，您应该希望在MySQL的未来版本中删除对它的支持。Consider using a simple 考虑对此类列使用简单的CHECK constraint instead for such columns.CHECK约束。
Using 使用FLOAT might give you some unexpected problems because all calculations in MySQL are done with double precision. FLOAT可能会给您带来一些意想不到的问题，因为MySQL中的所有计算都是以双精度完成的。See Section B.3.4.7, “Solving Problems with No Matching Rows”.请参见第B.3.4.7节，“解决没有匹配行的问题”。
FLOAT(p) [UNSIGNED] [ZEROFILL]
A floating-point number. 浮点数。p represents the precision in bits, but MySQL uses this value only to determine whether to use FLOAT or DOUBLE for the resulting data type. p表示以位为单位的精度，但是MySQL使用这个值只是为了确定对结果数据类型使用FLOAT还是DOUBLE。If 如果p is from 0 to 24, the data type becomes FLOAT with no M or D values. p从0到24，则数据类型将变为无M或D值的FLOAT。If 如果p is from 25 to 53, the data type becomes DOUBLE with no M or D values. p是从25到53，则数据类型变为DOUBLE，没有M或D值。The range of the resulting column is the same as for the single-precision 结果列的范围与本节前面介绍的单精度FLOAT or double-precision DOUBLE data types described earlier in this section.FLOAT或双精度DOUBLE数据类型的范围相同。
UNSIGNED, if specified, disallows negative values. UNSIGNED，则不允许负值。As of MySQL 8.0.17, the 从MySQL 8.0.17开始，UNSIGNED attribute is deprecated for columns of type FLOAT (and any synonyms) and you should expect support for it to be removed in a future version of MySQL. UNSIGNED属性对于FLOAT类型的列（以及任何同义词）都是不推荐的，您应该希望在MySQL的未来版本中删除对它的支持。Consider using a simple 考虑对此类列使用简单的CHECK constraint instead for such columns.CHECK约束。
FLOAT( syntax is provided for ODBC compatibility.p)FLOAT(语法。p)
DOUBLE[(M,D)] [UNSIGNED] [ZEROFILL]
A normal-size (double-precision) floating-point number. 一个正常大小（双精度）的浮点数。Permissible values are 允许值为-1.7976931348623157E+308 to -2.2250738585072014E-308, 0, and 2.2250738585072014E-308 to 1.7976931348623157E+308. -1.7976931348623157E+308至-2.2250738585072014E-308、0和2.2250738585072014E-308至1.7976931348623157E+308。These are the theoretical limits, based on the IEEE standard. 这些是基于IEEE标准的理论极限。The actual range might be slightly smaller depending on your hardware or operating system.根据硬件或操作系统的不同，实际范围可能会稍微小一些。
M is the total number of digits and D is the number of digits following the decimal point. M是总位数，D是小数点后的位数。If 如果省略M and D are omitted, values are stored to the limits permitted by the hardware. M和D，则将值存储到硬件允许的限制范围内。A double-precision floating-point number is accurate to approximately 15 decimal places.双精度浮点数精确到大约15位小数。
DOUBLE(M,D) is a nonstandard MySQL extension. 是一个非标准的MySQL扩展。As of MySQL 8.0.17, this syntax is deprecated and you should expect support for it to be removed in a future version of MySQL.从MySQL8.0.17开始，这种语法已经被弃用，您应该期望在MySQL8的未来版本中删除对它的支持。
UNSIGNED, if specified, disallows negative values. UNSIGNED，则不允许负值。As of MySQL 8.0.17, the 从MySQL 8.0.17开始，UNSIGNED attribute is deprecated for columns of type DOUBLE (and any synonyms) and you should expect support for it to be removed in a future version of MySQL. UNSIGNED属性对于DOUBLE类型的列（以及任何同义词）是不受欢迎的，您应该希望在将来的MySQL版本中删除对它的支持。Consider using a simple 考虑对此类列使用简单的CHECK constraint instead for such columns.CHECK约束。
DOUBLE PRECISION[(, M,D)] [UNSIGNED] [ZEROFILL]REAL[(M,D)] [UNSIGNED] [ZEROFILL]
These types are synonyms for 这些类型是DOUBLE. DOUBLE的同义词。Exception: If the 例外：如果启用了REAL_AS_FLOAT SQL mode is enabled, REAL is a synonym for FLOAT rather than DOUBLE.REAL_AS_FLOAT SQL模式，则REAL是FLOAT的同义词，而不是DOUBLE的同义词。