what is the primary key of a table?

[jerryt]

Hi there,

I'm using Helsinki and I'm wondering what is the primary key in a table.

It looks that most of the tables have a column 'sys_id', which seems like the primary key in that table. When I navigate to 'Tables and Columns', I see a big blue circle icon with an 'i' inside beside sys_id:

But some tables don't have sys_id. For example, pa_favorites and v_db_index seem not to have primary keys.

There's another interesting table. ts_word_roots has 3 columns and they are like this:

So my questions are:

1. How can I check what is the primary key in a table? (usually sys_id I guess, but I'm not sure)

2. Are there any tables without primary keys? (like pa_favorites and v_db_index?)

3. For table ts_word_roots, does it have a composite primary key?

Thanks a lot!

[Chuck Tomasi]

[jerryt]

That's weird, I really don't see sys_id in that table. Here's the response from mysandbox.service-now.com/v_db_index.do?SCHEMA:

<v_db_index>

      <element name="column_names" internal_type="string" max_length="1000" choice_list="false"/>

      <element name="table_name" internal_type="table_name" max_length="80" choice_list="false"/>

      <element name="index_name" internal_type="string" max_length="80" choice_list="false"/>

</v_db_index>

As you can see, there're only 3 columns show up.

In the picture above, I do see the primary key is sys_id, but it's just invisible. Is it an inaccessible column?

[Chuck Tomasi]

Because it starts with v_, it denotes a database view. That makes it special. I don't know the technical underpinnings of how database views work. Suffice it to say, MySQL's desc command isn't lying to me.

Anything else?

[jerryt]

I see, thanks man.

[jerryt]

Oh how about the table ts_word_roots? It has 3 indexed columns, so does it have a primary key consisting of all the 3 columns? Thanks