relation

utf8_bin vs. utf_unicode_ci

由 ℡╲_俬逩灬. 提交于 2019-11-27 20:25:38
My table Website Website_Name//column name Google Facebook Twitter Orkut Frype Skype Yahoo Wikipedia I i use utf8_bin collation then my query to search wikipedia in Website is Select Website_Name from Website where lower(Website_Name)='wikipedia' And if i use utf8_unicode_ci then my select query to search wikipedia in Website is Select Website_Name from Website where Website_Name='wikipedia' Now I want to know which collation is best depending upon the following queries Delan Azabani It depends on what you need. The utf8_bin collation compares strings based purely on their Unicode code point

Many tables or rows, which one is more efficient in SQL?

由 别说谁变了你拦得住时间么 提交于 2019-11-27 15:05:31
问题 I'm building a program that stores news headlines for companies and its timestamp from various sources. Let's say the number of company is 1000. It goes like Apple, Google, Microsoft.. etc. So I can think about two options. One table with numerous rows (above code is just an example). CREATE TABLE news ( news_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, company VARCHAR(10) NOT NULL, timestamp TIMESTAMP NOT NULL, source TEXT NOT NULL, content TEXT NOT NULL, ... ) // I also can make company and

How to find all the relations between all mysql tables?

由 天涯浪子 提交于 2019-11-27 12:06:54
How to find all the relations between all MySQL tables? If for example, I want to know the relation of tables in a database of having around 100 tables. Is there anyway to know this? The better way, programmatically speaking, is gathering data from INFORMATION_SCHEMA.KEY_COLUMN_USAGE table as follows: SELECT `TABLE_SCHEMA`, -- Foreign key schema `TABLE_NAME`, -- Foreign key table `COLUMN_NAME`, -- Foreign key column `REFERENCED_TABLE_SCHEMA`, -- Origin key schema `REFERENCED_TABLE_NAME`, -- Origin key table `REFERENCED_COLUMN_NAME` -- Origin key column FROM `INFORMATION_SCHEMA`.`KEY_COLUMN

Implementing one-to-zero-or-one relation in SQL Server

由 淺唱寂寞╮ 提交于 2019-11-27 08:42:28
I'm using Entity Framework 4.1 database first approach. I've used legacy database. In my edmx file which created entity classes based on tables in the legacy database, there is a one-to-zero-or-one association between some entities. Although I explored the tables of database and relation between them I didn't find out how one-to-zero-or-one relation have been implemented in database. For more information I put some screenshots of my database diagram and the property of its relation and correspondent entities in edmx file: The 1-0..1 relation in your database is directly visible. It is built

SQL ON DELETE CASCADE, Which Way Does the Deletion Occur?

由 て烟熏妆下的殇ゞ 提交于 2019-11-27 06:13:10
If I have two relations in a database, like this: CREATE TABLE Courses ( CourseID int NOT NULL PRIMARY KEY, Course VARCHAR(63) NOT NULL UNIQUE, Code CHAR(4) NOT NULL UNIQUE ); CREATE TABLE BookCourses ( EntryID int NOT NULL PRIMARY KEY, BookID int NOT NULL, Course CHAR(4) NOT NULL, CourseNum CHAR(3) NOT NULL, CourseSec CHAR(1) NOT NULL ); and I establish a foreign key relationship between the two, like this: ALTER TABLE BookCourses ADD FOREIGN KEY (Course) REFERENCES Courses(Code) ON DELETE CASCADE; Then you can see that the Course attribute in the BookCourses relation references the Code

How to return an empty ActiveRecord relation?

由 送分小仙女□ 提交于 2019-11-26 23:48:02
问题 If I have a scope with a lambda and it takes an argument, depending on the value of the argument, I might know that there will not be any matches, but I still want to return a relation, not an empty array: scope :for_users, lambda { |users| users.any? ? where("user_id IN (?)", users.map(&:id).join(',')) : [] } What I really want is a "none" method, the opposite of "all", that returns a relation that can still be chained, but results in the query being short-circuited. 回答1: There is a now a

How to find all the relations between all mysql tables?

由 你离开我真会死。 提交于 2019-11-26 15:41:30
问题 How to find all the relations between all MySQL tables? If for example, I want to know the relation of tables in a database of having around 100 tables. Is there anyway to know this? 回答1: The better way, programmatically speaking, is gathering data from INFORMATION_SCHEMA.KEY_COLUMN_USAGE table as follows: SELECT `TABLE_SCHEMA`, -- Foreign key schema `TABLE_NAME`, -- Foreign key table `COLUMN_NAME`, -- Foreign key column `REFERENCED_TABLE_SCHEMA`, -- Origin key schema `REFERENCED_TABLE_NAME`,

SQL ON DELETE CASCADE, Which Way Does the Deletion Occur?

由 独自空忆成欢 提交于 2019-11-26 11:54:46
问题 If I have two relations in a database, like this: CREATE TABLE Courses ( CourseID int NOT NULL PRIMARY KEY, Course VARCHAR(63) NOT NULL UNIQUE, Code CHAR(4) NOT NULL UNIQUE ); CREATE TABLE BookCourses ( EntryID int NOT NULL PRIMARY KEY, BookID int NOT NULL, Course CHAR(4) NOT NULL, CourseNum CHAR(3) NOT NULL, CourseSec CHAR(1) NOT NULL ); and I establish a foreign key relationship between the two, like this: ALTER TABLE BookCourses ADD FOREIGN KEY (Course) REFERENCES Courses(Code) ON DELETE
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