mysql中列信息查询(information
当前数据库中当前用户可以访问的每一个列在该视图中占一行。 INFORMATION_SCHEMA.COLUMNS 视图以 sysobjects 、 spt_data type_info 、 systypes 、 syscolumns 、 syscomments 、 sysconfigures 以及 syscharsets 系统表为基
当前数据库中当前用户可以访问的每一个列在该视图中占一行。INFORMATION_SCHEMA.COLUMNS 视图以 sysobjects、spt_data type_info、systypes、syscolumns、syscomments、sysconfigures 以及 syscharsets 系统表为基础。
若要从这些视图中检索信息,请指定完全合格的 INFORMATION_SCHEMA view_name 名称。
列名 | 数据类型 | 描述 |
---|---|---|
TABLE_CATALOG | nvarchar(128) | 表限定符。 |
TABLE_SCHEMA | nvarchar(128) | 表所有者。 |
TABLE_NAME | nvarchar(128) | 表名。 |
COLUMN_NAME | nvarchar(128) | 列名。 |
ORDINAL_POSITION | smallint | 列标识号。 |
COLUMN_DEFAULT | nvarchar(4000) | 列的默认值。 |
IS_NULLABLE | varchar(3) | 列的为空性。如果列允许 NULL,那么该列返回 YES。否则,返回 NO。 |
DATA_TYPE | nvarchar(128) | 系统提供的数据类型。 |
CHARACTER_MAXIMUM_LENGTH | smallint | 以字符为单位的最大长度,适于二进制数据、字符数据,或者文本和图像数据。否则,返回 NULL。有关更多信息,请参见数据类型。 |
CHARACTER_OCTET_LENGTH | smallint | 以字节为单位的最大长度,适于二进制数据、字符数据,或者文本和图像数据。否则,返回 NULL。 |
NUMERIC_PRECISION | tinyint | 近似数字数据、精确数字数据、整型数据或货币数据的精度。否则,返回 NULL。 |
NUMERIC_PRECISION_RADIX | smallint | 近似数字数据、精确数字数据、整型数据或货币数据的精度基数。否则,返回 NULL。 |
NUMERIC_SCALE | tinyint | 近似数字数据、精确数字数据、整数数据或货币数据的小数位数。否则,返回 NULL。 |
DATETIME_PRECISION | smallint | datetime 及 SQL-92interval 数据类型的子类型代码。对于其它数据类型,返回 NULL。 |
CHARACTER_SET_CATALOG | varchar(6) | 如果列是字符数据或 text 数据类型,那么返回 master,指明字符集所在的数据库。否则,返回 NULL。 |
CHARACTER_SET_SCHEMA | varchar(3) | 如果列是字符数据或 text 数据类型,那么返回 DBO,指明字符集的所有者名称。否则,返回 NULL。 |
CHARACTER_SET_NAME | nvarchar(128) | 如果该列是字符数据或 text 数据类型,那么为字符集返回唯一的名称。否则,返回 NULL。 |
COLLATION_CATALOG | varchar(6) | 如果列是字符数据或 text 数据类型,那么返回 master,指明在其中定义排序次序的数据库。否则此列为 NULL。 |
COLLATION_SCHEMA | varchar(3) | 返回 DBO,为字符数据或 text数据类型指明排序次序的所有者。否则,返回 NULL。 |
COLLATION_NAME | nvarchar(128) | 如果列是字符数据或 text 数据类型,那么为排序次序返回唯一的名称。否则,返回 NULL。 |
DOMAIN_CATALOG | nvarchar(128) | 如果列是一种用户定义数据类型,那么该列是某个数据库名称,在该数据库名中创建了这种用户定义数据类型。否则,返回 NULL。 |
DOMAIN_SCHEMA | nvarchar(128) | 如果列是一种用户定义数据类型,那么该列是这种用户定义数据类型的创建者。否则,返回 NULL。 |
DOMAIN_NAME | nvarchar(128) | 如果列是一种用户定义数据类型,那么该列是这种用户定义数据类型的名称。否则,返回 NULL。 |

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.
