Detailed explanation of MySQL data types: What you need to know

MySQL is one of the most popular relational database management systems in the world and is widely used because of its reliability, high security, high scalability and relatively low cost. MySQL data types define the storage methods of various data types and are an important part of MySQL. This article will explain in detail the data types of MySQL and some knowledge points that need to be paid attention to in practical applications.

1. MySQL data type classification

MySQL data types can be divided into the following categories:

1. Integer types: including TINYINT, SMALLINT, MEDIUMINT, INT , BIGINT, etc., used to store integer data.
2. Floating point types: including FLOAT, DOUBLE, DECIMAL, etc., used to store floating point data.
3. Date and time types: including DATE, TIME, YEAR, DATETIME and TIMESTAMP, etc., used to store date and time data.
4. String types: including CHAR, VARCHAR, TINYTEXT, TEXT, MEDIUMTEXT, LONGTEXT, etc., used to store character data.
5. Binary data types: including BINARY, VARBINARY, TINYBLOB, BLOB, MEDIUMBLOB, LONGBLOB, etc., used to store binary data.

2. Use of integer types

MySQL has many integer types, as follows:

1. TINYINT: occupies 1 byte, range is -128 to 127.
2. SMALLINT: Occupies 2 bytes, ranging from -32768 to 32767.
3. MEDIUMINT: Occupies 3 bytes, ranging from -8388608 to 8388607.
4. INT: Occupies 4 bytes, ranging from -2147483648 to 2147483647.
5. BIGINT: Occupies 8 bytes, ranging from -9223372036854775808 to 9223372036854775807.

You need to pay attention to the following points when using integer types:

1. When designing the table structure, you should choose different integer types according to actual needs. If the amount of data is small, you can use TINYINT or SMALLINT, if the amount of data is large, you can use BIGINT.
2. If you need to store unsigned integers, you can add the UNSIGNED keyword after the data type to avoid negative numbers.
3. Integer types are more efficient in querying, sorting and comparison.

3. Use of floating-point number types

MySQL has three floating-point number types, as follows:

1. FLOAT: occupies 4 bytes, Represents a single-precision floating point number with a precision of 7 digits.
2. DOUBLE: occupies 8 bytes and represents a double-precision floating point number with a precision of 15 digits.
3. DECIMAL: Used for precise calculations, storing numbers according to user-defined precision. The precision of DECIMAL is defined in terms of M and D, where M represents the total number of digits in the number and D represents the number of digits in the decimal part.

When using floating-point number types, you need to pay attention to the following points:

1. Floating-point number types may suffer from loss of precision during storage and calculation, so they are not suitable for use in situations involving Precisely calculated scenarios.
2. When using the DECIMAL type, you need to pay attention to its precision settings to avoid precision loss or errors.

4. Use of date and time types

MySQL has five date and time types, as follows:

1. DATE: used for storage Date, format is YYYY-MM-DD.
2. TIME: used to store time in the format of HH:MM:SS.
3. YEAR: Used to store the year in YYYY format.
4. DATETIME: used to store date and time in the format YYYY-MM-DD HH:MM:SS.
5. TIMESTAMP: Used to store date and time in the format YYYY-MM-DD HH:MM:SS, which can be updated automatically.

You need to pay attention to the following points when using date and time types:

1. DATE, TIME and DATETIME types can set default values ​​and constraints so that when inserting data Ensure data integrity and correctness.
2. TIMESTAMP type can be automatically updated when inserting data, which can avoid the cumbersome operation of manual update. But it should be noted that if you need to save a precise timestamp, you should use the DATETIME type.

5. Use of string types

MySQL has many string types, as follows:

1. CHAR: fixed-length string, Maximum length is 255 characters.
2. VARCHAR: variable-length string, the maximum length is 65535 characters.
3. TINYTEXT: Text with a maximum length of 255 characters.
4. TEXT: Text with a maximum length of 65535 characters.
5. MEDIUMTEXT: Text with a maximum length of 16777215 characters.
6. LONGTEXT: Text with a maximum length of 4294967295 characters.

When using string types, you need to pay attention to the following points:

1. When selecting string types, you should choose different types according to actual needs. If the length of the string is fixed, you can use the CHAR type; if the length is uncertain, you can use the VARCHAR type.
2. The storage efficiency of the VARCHAR type is higher than that of the CHAR type, but it is less efficient when querying and sorting.
3. If you need to store larger text, you should use the TEXT type instead of the VARCHAR type.

6. Use of binary data types

MySQL has many binary data types, as follows:

1. BINARY: Fixed-length binary data, the maximum length is 255 bytes.
2. VARBINARY: Variable-length binary data, the maximum length is 65535 bytes.
3. TINYBLOB: Binary data with a maximum length of 255 bytes.
4. BLOB: Binary data with a maximum length of 65535 bytes.
5. MEDIUMBLOB: Binary data with a maximum length of 16777215 bytes.
6. LONGBLOB: Binary data with a maximum length of 4294967295 bytes.

You need to pay attention to the following points when using binary data types:

1. When designing the table structure, you should choose different binary data types according to actual needs. If the amount of data is small, you can use TINYBLOB or BINARY, if the amount of data is large, you can use LONGBLOB or VARBINARY.
2. Binary data types are more efficient when storing and querying, but less efficient when sorting and comparing.

7. Summary

MySQL data types are an important part of designing table structures and storing data. Different data types have different characteristics and application scenarios. Understanding the data types of MySQL can help us better choose the appropriate data type to improve database performance and data storage efficiency, and use MySQL more efficiently in practical applications.

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