--20170505 --塗聚文 Geovin Du CREATE DATABASE DuMailSystem GO USE DuMailSystem GO --1查詢表的及备注说明 SELECT Sysobjects.name AS TABLE_NAME, syscolumns.Id, syscolumns.name AS COLUMN_NAME, systypes.name AS DATA_TYPE, syscolumns.length as CHARACTER_MAXIMUM_LENGTH…

这句话的意思是,两张表之间的外键找不到,首先看看外键设置正确了没,如果外键没问题,看看是不是_tablename_设置了没,就是再model中,定义类的时候,表格名称要_tablename_设置一下,不设置,有时候也会报这个错.…

A primary key is defined as a column or a group of column that their value are always be unique. Normally, NULL value will never be allowed in this column to be part of this column’s records. EXAMPLE : Let’s say we want to create a table name Users.…

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oreign key constraints (also known as referential constraints or referential integrity constraints) enable you to define required relationships between and within tables. For example, a typical foreign key constraint might state that every employee i…

What I would like to do is to display a single form that lets the user: Enter a document title (from Document model) Select one of their user_defined_code choices from a drop down list (populated by the UserDefinedCode model) Type in a unique_code (s…

在stackoverflow找到答案: DATABASES = { 'default': { ... 'OPTIONS': { "init_command": "SET foreign_key_checks = 0;", }, } } (According to the official doc) In previous versions of Django, fixtures with forward references (i.e. relations to r…

ntroduction to MySQL foreign key A foreign key is a field in a table that matches another field of another table. A foreign key places constraints on data in the related tables, which enables MySQL to maintain referential integrity. Let’s take a look…

ALTER TABLE `fd_rel_customer_doctor` ADD CONSTRAINT `FK_fd_rel_customer_doctor_1` FOREIGN KEY (`CUSTOMER_USER_ID`) REFERENCES `fd_customer_user` (`CUSTOMER_USER_ID`), ADD CONSTRAINT `FK_fd_rel_customer_doctor_2` FOREIGN KEY (`DOCTOR_ID`) REFERENCES `…

外键: 查询:select object_name(a.parent_object_id) 'tables'  from sys.foreign_keys a  where a.referenced_object_id=object_id('B表') 格式(名称):FK_A表_B表 A表是主表,引用B表的id字段作为外键,删除B表时候,“无法截断表B,因为该表正由 FOREIGN KEY 约束引用.” 删除外键: alert table A表 drop constraint FK_A表_B表 清…