欢迎进入Windows社区论坛,与300万技术人员互动交流 >>进入 14、游标 /* * 声明游标: * DECLARE 游标名 CURSOR FOR T_SQL; * *打开游标: *OPEN 游标名 * *关闭游标: *CLOSE 游标名 * *删除游标: *DEALLOCATE 游标名 * *游标读取数据: *FETCH NEXT FROM 游标
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14、游标
/*
* 声明游标:
* DECLARE 游标名 CURSOR FOR T_SQL;
*
*打开游标:
*OPEN 游标名
*
*关闭游标:
*CLOSE 游标名
*
*删除游标:
*DEALLOCATE 游标名
*
*游标读取数据:
*FETCH NEXT FROM 游标名
*(或者)Fetch FIRST from 游标名
*/
--声明游标
DECLARE deleteTable CURSOR FOR
SELECT ltrim(rtrim(NAME)) FROM Sysobjects WHERE NAME LIKE '%000079'
--打开游标
OPEN deleteTable
--关闭游标
CLOSE deleteTable
--删除游标
DEALLOCATE deleteTable
--读取数据
FETCH NEXT FROM deleteTable INTO @Value1,@Value2
--或则 Fetch first from mycursor
--判断游标是否存在 deleteTable:游标名
if cursor_status('global','deleteTable')=-3 and cursor_status('local','deleteTable')=-3
print '不存在'
else
print '存在'
CREATE PROC PROC_EA
AS
BEGIN
DECLARE EAMCMT4 CURSOR FOR
SELECT TOP 545 UserId,CreateTime FROM EA_MCMT4 ORDER BY CreateTime DESC
DECLARE @UserId nchar(50), @DateTime smallDatetime, @Id int
SET @Id = 560
OPEN EAMCMT4
WHILE @@FETCH_STATUS = 0
BEGIn
FETCH NEXT FROM EAMCMT4 INTO @UserId,@DateTime
UPDATE EA SET userId=@UserId,[DateTime]= @DateTime WHERE Id=@Id
SET @Id = @Id + 1
END
CLOSE EAMCMT4
DEALLOCATE EAMCMT4
END
GO
--清空日志
DUMP TRANSACTION DBName WITH NO_LOG
--收缩数据库文件
DBCC SHRINKFILE('dazhou_Log',1)
/*
*由此推导出SQLserver分页语句
*pageSize: 每页显示数据条数
*TableName:查询表名
*pageIndex:分页索引(默认为1,即首页)
*pageCount: 总页数
*/
IF pageIndex > 0 AND pageIndex
BEGIN
SELECT TOP pageSize * FROM TableName tn WHERE tn.ID NOT IN(
SELECT TOP (pageIndex-1)*pageSize tn.ID FROM TableName tn ORDER BY tn.ID ASC)
ORDER BY tn.ID ASC
END
ELSE
BEGIN
SELECT TOP pageSize * FROM TableName
END
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InnoDBBufferPool reduces disk I/O by caching data and indexing pages, improving database performance. Its working principle includes: 1. Data reading: Read data from BufferPool; 2. Data writing: After modifying the data, write to BufferPool and refresh it to disk regularly; 3. Cache management: Use the LRU algorithm to manage cache pages; 4. Reading mechanism: Load adjacent data pages in advance. By sizing the BufferPool and using multiple instances, database performance can be optimized.

Compared with other programming languages, MySQL is mainly used to store and manage data, while other languages such as Python, Java, and C are used for logical processing and application development. MySQL is known for its high performance, scalability and cross-platform support, suitable for data management needs, while other languages have advantages in their respective fields such as data analytics, enterprise applications, and system programming.

MySQL is worth learning because it is a powerful open source database management system suitable for data storage, management and analysis. 1) MySQL is a relational database that uses SQL to operate data and is suitable for structured data management. 2) The SQL language is the key to interacting with MySQL and supports CRUD operations. 3) The working principle of MySQL includes client/server architecture, storage engine and query optimizer. 4) Basic usage includes creating databases and tables, and advanced usage involves joining tables using JOIN. 5) Common errors include syntax errors and permission issues, and debugging skills include checking syntax and using EXPLAIN commands. 6) Performance optimization involves the use of indexes, optimization of SQL statements and regular maintenance of databases.

MySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.

MySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.

MySQL is an open source relational database management system that is widely used in Web development. Its key features include: 1. Supports multiple storage engines, such as InnoDB and MyISAM, suitable for different scenarios; 2. Provides master-slave replication functions to facilitate load balancing and data backup; 3. Improve query efficiency through query optimization and index use.

SQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.

The basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA


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