Selecting the right data type in MySQL can improve performance and storage efficiency. 1. Select fixed-length CHAR or variable-length VARCHAR according to the field length, and use TINYINT in the status field first; 2. Use DATE, DATETIME or TIMESTAMP for the time type as required to avoid using INT to store timestamps; 3. Use TEXT/BLOB to prioritize VARCHAR to reduce I/O overhead; 4. Use ENUM type or independent table to enumerate values to improve data standardization and query efficiency.
Selecting the appropriate data type in MySQL directly affects the performance, storage efficiency, and maintainability of the database. When many people first start writing table structures, they often choose VARCHAR(255) or INT just by just choosing, but in fact, each data type has its applicable scenarios. If you choose the right one, it can save space and improve query speed; if you choose the wrong one, it may slow down the entire system.
1. Select the appropriate type according to the length of the field content
MySQL provides a variety of string and numeric types, such as CHAR , VARCHAR , TEXT , TINYINT , INT , BIGINT , etc. The key to choosing these types is to estimate the maximum length and range of variation of the field content .
-
Fixed length vs. change length:
- If the field length is basically fixed (such as mobile phone number, ID number), it is more appropriate to use
CHAR(N), although it will occupy fixed space. - If the length difference is large (such as username, description information), it is more suitable for
VARCHAR(N), which only takes up the actual space used.
- If the field length is basically fixed (such as mobile phone number, ID number), it is more appropriate to use
-
Numeric type:
- For example, the status field usually has only a few values, and using
TINYINTis enough. There is no need to useINT, which saves space and reduces I/O pressure.
- For example, the status field usually has only a few values, and using
For example, if you have a field that represents "gender", you can use ENUM('male', 'female') or TINYINT , but it is much more efficient than using VARCHAR(10) .
2. Pay attention to the accuracy and purpose of time type
MySQL provides time-related types such as DATE , DATETIME , and TIMESTAMP . They each have applicable scenarios:
- DATE: Only the date is saved, the format is
YYYY-MM-DD, which is suitable for birthdays, deadlines, etc., where time is not required. - DATETIME: Stores date and time, with a larger range (from 1000 to 9999), suitable for recording creation or update time.
- TIMESTAMP: Similar to DATETIME, but has automatic update function and is affected by time zone. Commonly used in fields that require automatic recording of operation time.
A common misunderstanding is to save time as INT type time stamp. Although this is convenient to handle in some languages, it can be cumbersome to do time comparisons or format output in SQL queries.
3. Avoid abuse of TEXT and BLOB types
TEXT and BLOB types are suitable for storing longer contents, such as article body, image binary data, etc. But they also have some disadvantages to note:
- Fields that use
TEXT/BLOBcannot be used as part of the index (unless you specify the prefix length). - Their data is usually not stored in the rows of the main table, but is stored separately and referenced as a pointer, which results in additional I/O overhead.
- Using such fields when sorting or grouping will result in significant performance degradation.
Therefore, if you do not have to store a large amount of text, try to replace TEXT with VARCHAR . For example, the user profile field is usually a few hundred words enough, and using VARCHAR(1000) is more suitable than TEXT .
4. Use enum types reasonably
For some fields with limited values, such as order status and user role, the input range can be limited by using ENUM type:
status ENUM('pending', 'processing', 'completed', 'cancelled')
The benefits of doing this are:
- More standardized data to avoid invalid value insertion
- Query statements can be more concise and clear
- In some cases, it is lighter than foreign key associations
However, it should also be noted that if enumeration values may be frequently expanded in the future, or state values may be shared between different tables, it is better to use independent state table foreign keys.
Basically that's it. Choosing the right data type is not complicated, but it is easy to ignore. As long as you judge based on the dimensions of field content, usage frequency, and storage requirements, you can write a more efficient table structure.
The above is the detailed content of Choosing Appropriate Data Types in MySQL. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
Performing logical backups using mysqldump in MySQL
Jul 06, 2025 am 02:55 AM
mysqldump is a common tool for performing logical backups of MySQL databases. It generates SQL files containing CREATE and INSERT statements to rebuild the database. 1. It does not back up the original file, but converts the database structure and content into portable SQL commands; 2. It is suitable for small databases or selective recovery, and is not suitable for fast recovery of TB-level data; 3. Common options include --single-transaction, --databases, --all-databases, --routines, etc.; 4. Use mysql command to import during recovery, and can turn off foreign key checks to improve speed; 5. It is recommended to test backup regularly, use compression, and automatic adjustment.
Handling NULL Values in MySQL Columns and Queries
Jul 05, 2025 am 02:46 AM
When handling NULL values ??in MySQL, please note: 1. When designing the table, the key fields are set to NOTNULL, and optional fields are allowed NULL; 2. ISNULL or ISNOTNULL must be used with = or !=; 3. IFNULL or COALESCE functions can be used to replace the display default values; 4. Be cautious when using NULL values ??directly when inserting or updating, and pay attention to the data source and ORM framework processing methods. NULL represents an unknown value and does not equal any value, including itself. Therefore, be careful when querying, counting, and connecting tables to avoid missing data or logical errors. Rational use of functions and constraints can effectively reduce interference caused by NULL.
Aggregating data with GROUP BY and HAVING clauses in MySQL
Jul 05, 2025 am 02:42 AM
GROUPBY is used to group data by field and perform aggregation operations, and HAVING is used to filter the results after grouping. For example, using GROUPBYcustomer_id can calculate the total consumption amount of each customer; using HAVING can filter out customers with a total consumption of more than 1,000. The non-aggregated fields after SELECT must appear in GROUPBY, and HAVING can be conditionally filtered using an alias or original expressions. Common techniques include counting the number of each group, grouping multiple fields, and filtering with multiple conditions.
Paginating Results with LIMIT and OFFSET in MySQL
Jul 05, 2025 am 02:41 AM
MySQL paging is commonly implemented using LIMIT and OFFSET, but its performance is poor under large data volume. 1. LIMIT controls the number of each page, OFFSET controls the starting position, and the syntax is LIMITNOFFSETM; 2. Performance problems are caused by excessive records and discarding OFFSET scans, resulting in low efficiency; 3. Optimization suggestions include using cursor paging, index acceleration, and lazy loading; 4. Cursor paging locates the starting point of the next page through the unique value of the last record of the previous page, avoiding OFFSET, which is suitable for "next page" operation, and is not suitable for random jumps.
Calculating Database and Table Sizes in MySQL
Jul 06, 2025 am 02:41 AM
To view the size of the MySQL database and table, you can query the information_schema directly or use the command line tool. 1. Check the entire database size: Execute the SQL statement SELECTtable_schemaAS'Database',SUM(data_length index_length)/1024/1024AS'Size(MB)'FROMinformation_schema.tablesGROUPBYtable_schema; you can get the total size of all databases, or add WHERE conditions to limit the specific database; 2. Check the single table size: use SELECTta
Setting up asynchronous primary-replica replication in MySQL
Jul 06, 2025 am 02:52 AM
To set up asynchronous master-slave replication for MySQL, follow these steps: 1. Prepare the master server, enable binary logs and set a unique server-id, create a replication user and record the current log location; 2. Use mysqldump to back up the master library data and import it to the slave server; 3. Configure the server-id and relay-log of the slave server, use the CHANGEMASTER command to connect to the master library and start the replication thread; 4. Check for common problems, such as network, permissions, data consistency and self-increase conflicts, and monitor replication delays. Follow the steps above to ensure that the configuration is completed correctly.
Implementing Transactions and Understanding ACID Properties in MySQL
Jul 08, 2025 am 02:50 AM
MySQL supports transaction processing, and uses the InnoDB storage engine to ensure data consistency and integrity. 1. Transactions are a set of SQL operations, either all succeed or all fail to roll back; 2. ACID attributes include atomicity, consistency, isolation and persistence; 3. The statements that manually control transactions are STARTTRANSACTION, COMMIT and ROLLBACK; 4. The four isolation levels include read not committed, read submitted, repeatable read and serialization; 5. Use transactions correctly to avoid long-term operation, turn off automatic commits, and reasonably handle locks and exceptions. Through these mechanisms, MySQL can achieve high reliability and concurrent control.
Handling character sets and collations issues in MySQL
Jul 08, 2025 am 02:51 AM
Character set and sorting rules issues are common when cross-platform migration or multi-person development, resulting in garbled code or inconsistent query. There are three core solutions: First, check and unify the character set of database, table, and fields to utf8mb4, view through SHOWCREATEDATABASE/TABLE, and modify it with ALTER statement; second, specify the utf8mb4 character set when the client connects, and set it in connection parameters or execute SETNAMES; third, select the sorting rules reasonably, and recommend using utf8mb4_unicode_ci to ensure the accuracy of comparison and sorting, and specify or modify it through ALTER when building the library and table.
