SQL(Structured Query Language,结构化查询语言)是使用关系模型的数据库应用语言, 与数据直接打交道 ,由 IBM 上世纪70年代开发出来。后由美国国家标准局(ANSI)开始着手制定SQL标准,先后有 SQL-86 , SQL-89 , SQL-92 , SQL-99 等标准。 SQL 有两个重要的标准,分别是 SQL92 和 SQL99,它们分别代表了 92 年...
FROM information_schema.tables WHERE table_schema = 'test' ORDER BY table_name DESC; 解释: 对表的meta data的查询需要使用information_schema.tables, table_schema是数据库的名称,table_name是具体的表明,table_type指的是表的类型 2. 检查数据库'test'中的某一个表'd_ad'是否存在 select count(1) from...
order by table_rows desc) as b where b.table_name like 'sj_demo%' or b.table_name like 'sj_onlyinv' 2.查询wangdaisj数据库里以sj_demo为开头的所有表的表明 SELECT table_name FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA ='wangdaisj' and table_name like 'sj_demo%'" information_s...
connection.query("SELECT DATABASE() AS tableSchema",function(error,results,fields){if(error)throwerror;// 处理查询结果}); 1. 2. 3. 4. 这里的"SELECT DATABASE() AS tableSchema"是查询语句,它将查询当前数据库的名字,并将结果命名为tableSchema。 4. 获取查询结果 在查询完成后,我们可以通过回调函...
TABLE_SCHEMA queryPosted by: Erik Lee Date: February 07, 2017 10:10PM select table_name, table_schema from information_schema.tables where TABLE_SCHEMA like 'Net%' -- Can someone point out why the TABLE_SCHEMA column is displayed like so:- db_structure.php?db=net_drupal8&...
A more accurate method of obtaining this information in such cases is to query the INFORMATION_SCHEMA PARTITIONS table, as shown in this example: SELECT SUM(DATA_FREE) FROM INFORMATION_SCHEMA.PARTITIONS WHERE TABLE_SCHEMA = 'mydb' AND TABLE_NAME = 'mytable'; For more information, see ...
代码语言:sql AI代码解释 -- 分析表 ANALYZE TABLE students; -- 优化表(重建表和索引) OPTIMIZE TABLE students; -- 检查表是否损坏 CHECK TABLE students; -- 修复表 REPAIR TABLE students;监控工具 MySQL性能模式(Performance Schema): 代码语言:sql AI代码解释 -- 启用性能模式 SET GLOBAL performance_schem...
查询缓存启用情况(SELECT * FROM mysql.query_cache_status;) 缓冲池命中率(SHOW ENGINE INNODB STATUS | grep buffer_pool) 锁等待统计(SELECT * FROM information_schema.innodb_locks;) 索引碎片分析(EXPLAIN ANALYZE) 临时表使用情况(SELECT * FROM mysql temptables;) ...
读取数据表 public static void searchAllTable() { //String sql="SELECT * FROM information_schema.`TABLES`"; String sql="select table_name from information_s sql mysql 读取数据 apache nifi mysql 数据表读取写入 数据库和文件系统的关系什么是文件系统, 操作系统用来管理磁盘的被称为文件系统像 InnoDB...
root@localhost : (none) 11:57:28> SELECT * FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE\G; *** 1. row *** QUERY: select * from sbtest.sbtest1 where id=1 TRACE: { "steps": [ { "join_preparation": { "select#": 1, "steps": [ {...