MySQL字段的取值范围
TINYINT -128 127 TINYINT UNSIGNED 0 255 SMALLINT -32768 32767 SMALLINT UNSIGNED 0 65535 MEDIUMINT -8388608 8388607 MEDIUMINT UNSIGNED 0 16777215 INT 或 INTEGER -2147483648 2147483647 INT UNSIGNED 或 INTEGER UNSIGNED 0 4294967295 BIGINT -92
TINYINT
-128 – 127
TINYINT UNSIGNED
0 – 255
SMALLINT
-32768 – 32767
SMALLINT UNSIGNED
0 – 65535
MEDIUMINT
-8388608 – 8388607
MEDIUMINT UNSIGNED
0 – 16777215
INT 或 INTEGER
-2147483648 – 2147483647
INT UNSIGNED 或 INTEGER UNSIGNED
0 – 4294967295
BIGINT
-9223372036854775808 – 9223372036854775807
BIGINT UNSIGNED
0 – 18446744073709551615
FLOAT
-3.402823466E+38 – -1.175494351E-38
0
1.175494351E-38 – 3.402823466E+38
DOUBLE 或 DOUBLE PRECISION 或 REAL
-1.7976931348623157E+308 – -2.2250738585072014E-308
0
2.2250738585072014E-308 – 1.7976931348623157E+308
DECIMAL[(M,[D])] 或 NUMERIC(M,D)
由M(整个数字的长度,包括小数点,小数点左边的位数,小数点右边的位数,但不包括负号)和D(小数点右边的位数)来决定,M缺省为10,D缺省为0
DATE
1000-01-01 – 9999-12-31
DATETIME
1000-01-01 00:00:00 – 9999-12-31 23:59:59
TIMESTAMP
1970-01-01 00:00:00 – 2037年的某天(具体是哪天我也不知道,呵呵)
TIME
-838:59:59′ to 838:59:59
YEAR[(2|4)]
缺省为4位格式,4位格式取值范围为1901 – 2155,0000,2位格式取值范围为70-69(1970-2069)
CHAR(M) [BINARY] 或 NCHAR(M) [BINARY]
M的范围为1 – 255,如果没有BINARY项,则不分大小写,NCHAR表示使用缺省的字符集.在数据库中以空格补足,但在取出来时末尾的空格将自动去掉.
[NATIONAL] VARCHAR(M) [BINARY]
M的范围为1 – 255.在数据库中末尾的空格将自动去掉.
TINYBLOB 或 TINYTEXT
255(2^8-1)个字符
BLOB 或 TEXT
65535(2^16-1)个字符
MEDIUMBLOB 或 MEDIUMTEXT
16777215 (2^24-1)个字符
LONGBLOB 或 LONGTEXT
4294967295 (2^32-1)个字符
ENUM(‘value1′,’value2′,…)
可以总共有65535个不同的值
SET(‘value1′,’value2′,…)
最多有64个成员
,
Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

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

Big data structure processing skills: Chunking: Break down the data set and process it in chunks to reduce memory consumption. Generator: Generate data items one by one without loading the entire data set, suitable for unlimited data sets. Streaming: Read files or query results line by line, suitable for large files or remote data. External storage: For very large data sets, store the data in a database or NoSQL.

MySQL query performance can be optimized by building indexes that reduce lookup time from linear complexity to logarithmic complexity. Use PreparedStatements to prevent SQL injection and improve query performance. Limit query results and reduce the amount of data processed by the server. Optimize join queries, including using appropriate join types, creating indexes, and considering using subqueries. Analyze queries to identify bottlenecks; use caching to reduce database load; optimize PHP code to minimize overhead.

Backing up and restoring a MySQL database in PHP can be achieved by following these steps: Back up the database: Use the mysqldump command to dump the database into a SQL file. Restore database: Use the mysql command to restore the database from SQL files.

How to insert data into MySQL table? Connect to the database: Use mysqli to establish a connection to the database. Prepare the SQL query: Write an INSERT statement to specify the columns and values to be inserted. Execute query: Use the query() method to execute the insertion query. If successful, a confirmation message will be output.

One of the major changes introduced in MySQL 8.4 (the latest LTS release as of 2024) is that the "MySQL Native Password" plugin is no longer enabled by default. Further, MySQL 9.0 removes this plugin completely. This change affects PHP and other app

To use MySQL stored procedures in PHP: Use PDO or the MySQLi extension to connect to a MySQL database. Prepare the statement to call the stored procedure. Execute the stored procedure. Process the result set (if the stored procedure returns results). Close the database connection.

Creating a MySQL table using PHP requires the following steps: Connect to the database. Create the database if it does not exist. Select a database. Create table. Execute the query. Close the connection.

Oracle database and MySQL are both databases based on the relational model, but Oracle is superior in terms of compatibility, scalability, data types and security; while MySQL focuses on speed and flexibility and is more suitable for small to medium-sized data sets. . ① Oracle provides a wide range of data types, ② provides advanced security features, ③ is suitable for enterprise-level applications; ① MySQL supports NoSQL data types, ② has fewer security measures, and ③ is suitable for small to medium-sized applications.
