Different Types of SQL Keys
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On junction tables, we use composite PRIMARY KEY which contains FOREIGN KEY reference to the parent tables. And for the other question, I will have to pass. This would give me an idea on how many tables I was dealing with. Every student may answer the survey, at most once a year.
Still table2 needs a PRIMARY KEY. Some sample data that illustrates the problem and desired solution could give people some clue in which direction to go.
Different Types of SQL Keys - But one should always carefully examine the data requirements to eliminate the viability of natural keys before adopting surrogate keys. He is a blogger, avid tweeter, and a frequent speaker at SQL Saturday's as well as other conferences.
You never know when the idea for a script will make an appearance. I had to work with composite primary keys recently while working on a project for a client. More specifically, I had to create a process that would dynamically dynamic SQL?! Usually, a primary key is just a single column that uniquely identifies a row within a table. However, a composite primary key consisting of 2 or more columns can be created. Regardless if the primary key is singular or composite, it provides identical functionality. In this particular instance, this process would perform data modifications based on the columns that composed the primary key. Thus I needed to be able to determine what columns are in the key. There is a limit to the number of columns you can have in a composite key. In , the limit is 32 columns and a primary key could have up to 16 columns. This would give me an idea on how many tables I was dealing with. Thankfully, SQL Server has this information by using system DMVs dynamic management views along with the function. Now I knew which tables had a primary key comprised of multiple columns as well as how many columns were in the key definition. Taking things a step further, I thought that it would be useful to see what columns the primary key is composed of in that same output. This part becomes a little more complicated to gather as we need to get the list of columns, which could be 1 — 32 columns or 1-16 columns depending on the version of SQL Server into a comma delimited list. Using the STUFF function along with XML PATH is a quick and efficient way to generate a comma delimited list of string values. Using a CTE, we can tie these two result sets together and get a clean unified look. This should be a cleaner look. The has been updated with this change. This query helped me in creating the process my client needed. It just might help you to figure out some logic when writing dynamic SQL! You can download the full script from. John Morehouse is currently a Database Architect with Farm Credit Mid-America out of Louisville, KY. He is a blogger, avid tweeter, and a frequent speaker at SQL Saturday's as well as other conferences. He is also heavily involved with the Professional Association of SQL Server PASS. In his spare time, you can usually find John reading up on SQL Server topics as well as chasing his two boys around the house.
You can use validation for this purpose. That is, you design the model, implement the database, then make your client work with it Option 1: Assuming an owner can have 0. Example : We can have a DeptID column in the Employee table which is pointing to DeptID column in a department table where it a primary key. This is a pain if you need to update or drop the PK as you have to first get the name from the db and then use dynamic sql or build the command in code first. If a primary key consists of two or more columns it is called a composite composite key in sql server key. This is done using SQL statements at the time of table creation. But two years later or so, I had to work with some code around these table. The latter is better to match the foreign key. For more help refer the article.
