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':...
AI代码解释 mysql>select*from grade;+---+---+---+---+|id|sno|courseName|grade|+---+---+---+---+|1|202001|高数一|90||2|202003|高数二|88||3|202003|英语一|77||4|202004|英语二|79||5|202002|C++语言设计|87||6|202005|Java面向对象基础|98||7|202006|算法分析与实现|76||8|2...
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 ...
mysql>mysql>CREATETABLEcourse(idINT(11)PRIMARYKEYAUTO_INCREMENT,nameVARCHAR(30)); Query OK,0rows affected (0.01sec) mysql>mysql>mysql>CREATETABLEteacher(->idINT(11)PRIMARYKEYAUTO_INCREMENT,->nameVARCHAR(30),->course_idINT(11)NOTNULL,->CONSTRAINTteacher_courseFOREIGNKEY(course_id)REFERENCEScourse...
2. 因为 LAST_INSERT_ID 是基于 Connection 的,只要每个线程都使用独立的 Connection 对象,LAST_INSERT_ID 函数 将返回该 Connection 对 AUTO_INCREMENT列 最新的 insert or update* 作生成的第一个record 的ID。这个值不能被其它客户端(Connection)影响,保证了你能够找回自己的 ID 而不用担心其它客户端的活动,...
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,...
CREATETABLE`tb_user`(`id`INT(11)NOTNULLAUTO_INCREMENT,`username`VARCHAR(50)NOTNULL,`password`VAR...
`id` int NOT NULL AUTO_INCREMENT, `flag` int NOT NULL, `value` varchar(20) NOT NULL, PRIMARY KEY (`id`), KEY `idx_a_flag` (`flag`) ) 测试1: 子查询 select flag from B where B_id<100 结果集99条 select * from A where flag in (select flag from B where B_id<100 ); 198...
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...