Is there any difference in performance (in terms of inserting/updating & querying) a table if the primary key is a single column (e.g., 开发者_StackOverflow社区a GUID generated for every row) or m
I created a model that had a string primary_key. The Create action in Ruby on Rails gave me the following error:
For a number of reasons I have to use a linked csv file in a sqlexpress database. Col1 is always u开发者_运维百科nique, although the data changes periodically, based on current logins.
For a number of reasons^, I\'d like to use a U开发者_运维问答UID as a primary key in some of my Django models. If I do so, will I still be able to use outside apps like \"contrib.comments\", \"django-
I am trying to run this query: ALTER TABLE table DROP PR开发者_如何学编程IMARY KEY, ADD PRIMARY KEY( `CUSTNO` , `DEPTNO` , `PRODNO` , `DT` );
I am seeing too frequently \"not null primary key\" in scripts creating tables in TSQL in blogs, articles, books, forums, here in SO, etc.
I\'m con开发者_StackOverflow中文版verting a MySQL table to PostgreSQL for the first time in my life and running into the traditional newbie problem of having no auto_increment.
I create the following table in H2: CREATE TABLE TEST (ID BIGINT NOT NULL PRIMARY KEY) Then I look into INFORMATION_SCHEMA.TABLES table:
What is开发者_开发知识库 the difference between Primary key And unique Key constraint? What\'s the use of it?? Both are used to denote candidate keys for a table.
I have a problem with MySql primary keys, it\'s for my project i\'m working on now! i have to have a unit name(not a number)as a key in my database, it is a combination of letters and numbers, i can\
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