1. select 查询 in、not in、exists、not exists 的区别 exists 效率远远大于 in CREATESEQUENCE "ioc_dw_second"."test0002_seq" INCREMENT1MINVALUE1MAXVALUE9223372036854775807START1CACHE1CYCLE ;CREATETABLE"ioc_dw_second"."test0002" ( "rid" int4NOTNULLDEFAULTnextval('"ioc_dw_second".test0002_seq':...
CREATE TABLE `A`(`id` int NOTNULLAUTO_INCREMENT,`flag` int NOTNULL,`value` varchar(20)NOTNULL,PRIMARY KEY(`id`),KEY `idx_a_flag`(`flag`)) 测试1: 子查询selectflagfromBwhereB_id<100结果集99条select*fromAwhereflagin(selectflagfromBwhereB_id<100);198rowsinset(0.00sec)select*fromAwhere...
9.SELECT INTO 语句 10.CREATE DATABASE 语句 11.CREATE TABLE 语句 12.SQL 约束 SQL NOT NULL 约束 SQL UNIQUE 约束 SQL PRIMARY KEY 约束 SQL FOREIGN KEY 约束 SQL CHECK 约束 SQL DEFAULT 约束 13.CREATE INDEX 语句(索引) 14.DROP 语句 15.ALTER TABLE 语句 16.AUTO INCREMENT 字段(自增) 17.SQL ...
IN和EXISTS被频繁使用在SQL中,虽然作用是一样的,但是在使用效率谁更高这点上众说纷纭。下面我们就通过一组测试来看,在不同场景下,使用哪个效率更高。 测试数据: B表: 大表,大约300000行数据 CREATE TABLE `B` ( `id` int NOT NULL AUTO_INCREMENT, `B_id` int NOT NULL, `value` varchar(20) NOT ...
除了用distinct还可以用not in 或者 not exists 实现,代码如下: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 //not inSELECTDISTINCTA.nameFROMStudentAWHEREA.name notin(SELECTDistinctS.nameFROMStudentSWHERES.score<80);//not existsSELECTDISTINCTA.name From StudentAwhere notexists(SELECT1From Stude...
SELECT ... 语句正常情况下为快照读,不加锁; SELECT ... LOCK IN SHARE MODE 语句为当前读,加 S 锁; SELECT ... FOR UPDATE 语句为当前读,加 X 锁; 常见的 DML 语句(如 INSERT、DELETE、UPDATE)为当前读,加 X 锁; 常见的 DDL 语句(如 ALTER、CREATE 等)加表级锁,且这些语句为隐式提交,不能回滚...
In another query window, execute the query without the [Productfeedback] column and capture the similar statistics. 在另一个查询窗口中,执行不带[Productfeedback]列的查询并捕获类似的统计信息。 SELECT [ProductID] ,[ProductName] ,[ProductLaunchDate] ...
increment uint64 Not_mandatory Size in MB to grow the file package0 event_file lazy_create_blob boolean Not_mandatory Create blob upon publishing of first event buffer, not before. package0 event_file max_file_size uint64 Not_mandatory Maximum file size in MB p...
Column 'd_text' in table 'datatype' have no comments. Auto increment column 'd_int' is meaningful? it's dangerous! SQL : create table datatype (d_tinyint tinyint, d_smallint smallint, d_mediumint mediumint, d_int int primary key auto_increment, d_bigint bigint, d_decimal decimal,...
CREATE TABLE `settlement_invoice_relation` (`id` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键ID',`invoice_code` varchar(255) DEFAULT NULL COMMENT '发票代码',`invoice_number` varchar(255) DEFAULT NULL COMMENT '发票号码',`settlement_bill_no` varchar(64) DEFAULT NULL COMMENT '结算单号',PRIM...