Since we can specify constraints on a table, there needs to be a way to remove this constraint as well. In SQL, this is done via the ALTER TABLE statement. The SQL syntax to remove a constraint from a table is, ALTER TABLE "table_name" DROP [CONSTRAINT|INDEX] "CONSTRAINT_NAME";...
SQL REPLACE SQL TO_DATE Date Functions SQL DDL SQL CREATE TABLE SQL Data Types SQL View SQL CREATE VIEW SQL Index SQL CREATE INDEX SQL DROP TABLE SQL TRUNCATE TABLE SQL USE SQL CREATE DATABASE SQL DROP DATABASE SQL GRANT SQL REVOKE SQL CONSTRAINT NOT NULL Constraint DEFAULT Constraint UNIQU...
比如以下的SQL语句:selectt1.*fromt_grxx t1wheredwbhIN(selectt2.dwbhfromt_dwxx t2); 由于子查询"select t2.dwbh from t_dwxx t2"的dwbh是PK,子查询提升后,t_grxx的dwbh只对应t_dwxx唯一的一条记录,因此可以把半连接转换为内连接,执行计划如下: testdb=# explain verbose select t1.*fromt_grxx ...
CONSTRAINT emlyee_dept_fk FOREIGN KEY(deptId) REFERENCES dept(id) 约束 外键名称 外键 参照 参考表(参考字段) 外键 多表的设计 一对多:(非常多) CREATE TABLE department( id int primary key, name varchar(100), floor int ); CREATE TABLE employee( id int primary key, name varchar(100), salary ...
CONSTRAINT `fktid` FOREIGN KEY (`tid`) REFERENCES `teacher` (`id`) ) ENGINE=INNODB DEFAULT CHARSET=utf8 INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('1', '小明', '1'); INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('2', '小红', '1'); ...
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8090/admin/confluence-collaborative-editor-plugin/configure.action | traceId: d0e2ba5342874779 | userName: admin org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: ...
# remove channel column from constraints batch_op.drop_constraint( "_conda_package_build_uc", ) # re-add the constraint without the channel column batch_op.create_unique_constraint( "_conda_package_build_uc", [ "package_id", "subdir", "build", "build_number", "sha256", ], ) # rem...
sql_str VARCHAR2(500); v_err_code NUMBER; v_err_msg VARCHAR2(200); BEGIN -- drop all reference constraints begin sql_str := 'select table_name,constraint_name from user_constraints where constraint_type=''R'''; EXECUTE IMMEDIATE sql_str BULK COLLECT INTO cst_tab_name,cst_name; FOR ...
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