[SQL Server Delete with Join]( [Understanding Foreign Key Constraint in SQL Server](
alter table test add constraint test_pk_id primarykey(id); 代码语言:javascript 代码运行次数:0 运行 AI代码解释 alter table test addcheck(genderin('F','M')); 5.删除约束: 语法:alter table tb_name drop 约束名。 例如: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 alter table test dro...
主键约束提示 --下面使用currval值,提示主键冲突,从PK_TB_CONS2_EMPNO即可得知是主键列冲突,这就是自定义约束名的好处 SQL> INSERT INTO tb_constraint...--外键约束对delete语句的影响: SQL> DELETE FROM tb_constraint_2; 2 rows deleted...外键约束对delete语句的影响: 删除主表数据时,如果从表有对该数据...
You can implement error handling for the DELETE statement by specifying the statement in aTRY...CATCHconstruct. TheDELETEstatement may fail if it violates a trigger or tries to remove a row referenced by data in another table with aFOREIGN KEYconstraint. If theDELETEremoves multiple rows, and ...
"update_time"timestamp(6)DEFAULTpg_systimestamp(),CONSTRAINT"test0002_pkey"PRIMARYKEY("rid") ) ; 表a 表 b exists SELECT*FROMioc_dw_second.test0001 aWHEREexists(SELECT*FROMioc_dw_second.test0002 bWHEREa.rid=b.rid ) in SELECT*FROMioc_dw_second.test0001 aWHEREridin(SELECTridFROMioc_dw_...
新增主键altertableempaddconstraintemp_pkprimarykey(id)--- 3.10 新增外键altertableempaddconstraintfk...
(1)数据定义(SQL DDL)用于定义SQL模式、基本表、视图和索引的创建和撤消操作。 SQL 的数据定义语言 (DDL) 部分使我们有能力创建或删除表格。我们也可以定义索引(键),规定表之间的链接,以及施加表间的约束。 SQL 中最重要的 DDL 语句: CREATE DATABASE- 创建新数据库 ...
New1:selecta.constraint_name,a.column_namefrom user_cons_columnsa,user_constraintsbwherea.table_name= upper('emp') CONSTRAINT_NAMECOLUMN_NAME --- PK_EMPNOEMPNO Isthereaprimarykeyconstraintinthelookuptable? BYS@bys1>selecta.constraint_name,a.column_namefrom user_cons_columns...
between two tables. A foreign key does this by requiring that values in the column on which it applies must already exist in the column that it references. In the following example, the foreign key constraint requires that any value added to theownerIDcolumn must already exist in thememberID...
mysqldump -u [username] –p[password] –no-create-info [database_name] > [dump_file.sql] 实例: mysqldump –u root –p123456 –no-create-info yiibaidb > D:\worksp\bakup\backup003.sql 多个数据库备份到一个文件夹: 如果要通过[database_name]中的命令来备份多个数据库,只需单独的数据库名称...