MYSQL存储过程中使用游标嵌套的实例 MySQL 存储过程 delimiter $$drop procedure if exists findErrorLifeRoute $$CREATE PROCEDURE findErrorLifeRoute() BEGINdeclare routeId,routeStopId BIGINT ; declare str,tmp_street VARCHAR(255) ; DECLARE l_done
MYSQL存储过程中使用游标嵌套的实例
MySQL 存储过程delimiter $$ drop procedure if exists findErrorLifeRoute $$ CREATE PROCEDURE findErrorLifeRoute() BEGIN declare routeId,routeStopId BIGINT ; declare str,tmp_street VARCHAR(255) ; DECLARE l_done,num,life,localId,tmp_localId INT DEFAULT 0; -- 声明两个游标,第二个游标使用到第一个的查询结果 DECLARE grade_csr cursor FOR SELECT route_id FROM routes where LIFE_CYCLE_STATUS<39998 and LIFE_CYCLE_STATUS>35001; DECLARE class_csr cursor FOR SELECT LOCATION_INNER_ID,STREET FROM route_stops WHERE ROUTE_ID=routeId order by STOP_NUMBER asc; DECLARE CONTINUE HANDLER FOR NOT FOUND SET l_done=1; OPEN grade_csr; -- 第一个循环 grade_loop: LOOP -- Loop through org_grade FETCH grade_csr into routeId; IF l_done=1 THEN LEAVE grade_loop; END IF; SET num=0; set tmp_street=null; set tmp_localId=0; OPEN class_csr; -- 第二个循环 class_loop: LOOP -- Loop through class in grade. FETCH class_csr INTO localId,str; IF l_done=1 THEN LEAVE class_loop; END IF; if localId =tmp_localId or (str is not null and str=tmp_street) THEN set tmp_street=str; set tmp_localId=localId; else set num=num+1; set tmp_street=str; set tmp_localId=localId; end if; -- 结束第一个循环 END LOOP class_loop; CLOSE class_csr; SET l_done=0; set life=36000+(num-1)*100+6; INSERT into route_tmp (select ROUTE_ID,LIFE_CYCLE_STATUS,num,life,ACCOUNT_ID,str from routes r where r.ROUTE_ID=routeId and LIFE_CYCLE_STATUS=life ); -- 结束第二个循环 END LOOP grade_loop; CLOSE grade_csr; END $$ delimiter ;

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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