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Can a foreign key be NULL and/or duplicate?
...mply requires that the value in that field must exist first in a different table (the parent table). That is all an FK is by definition. Null by definition is not a value. Null means that we do not yet know what the value is.
Let me give you a real life example. Suppose you have a database that sto...
Why should hash functions use a prime number modulus?
A long time ago, I bought a data structures book off the bargain table for $1.25. In it, the explanation for a hashing function said that it should ultimately mod by a prime number because of "the nature of math".
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Count table rows
What is the MySQL command to retrieve the count of records in a table?
11 Answers
11
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Html table tr inside td
I am trying to create a table in HTML. I have the following design to create. I had added a <tr> inside the <td> but somehow the table is not created as per the design.
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How to get all columns' names for all the tables in MySQL?
Is there a fast way of getting all column names from all tables in MySQL , without having to list all the tables?
10 Answe...
Vertically align text next to an image?
...lt;/div>
Multiple-lines vertical-align:middle
<div style="display:table;width:30px;height:60px;">
<div style="display:table-cell;height:30px;">This is positioned in the middle</div>
</div>
If you must support ancient versions of IE <= 7
In order to get this to w...
How do HashTables deal with collisions?
I've heard in my degree classes that a HashTable will place a new entry into the 'next available' bucket if the new Key entry collides with another.
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How to export table as CSV with headings on Postgresql?
I'm trying to export a PostgreSQL table with headings to a CSV file via command line, however I get it to export to CSV file, but without headings.
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How do I show the schema of a table in a MySQL database?
From the MySQL console, what command displays the schema of any given table?
5 Answers
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Vertically centering a div inside another div [duplicate]
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tl;dr
Vertical align middle works, but you will have to use table-cell on your parent element and inline-block on the child.
This solution is not going to work in IE6 & 7. Yours is the safer way to go for those. But since you tagged your question with CSS3 and HTML5 I was thinkin...