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What is a Hash Key?

M. McGee
Updated May 16, 2024
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A hash key is a small value that is used to represent a large piece of data in a hash system. A hash function is a mathematical equation that simplifies large amounts of data into small values. This process saves space in a database and makes retrieving information faster and easier for the programs. It is also common to use hash systems to locate repeating information in complex systems, like a repeated voice or image pattern or even repeated portions of a genome or deoxyribonucleic acid DNA strand. In addition, hash key is the international English term for the # key on a telephone or keyboard.

A hash system works via a mathematical system that turns information into a series of numerical hash keys. The original information for each hash key is saved in a listing called a hash table. When a system looks for information, but finds a key instead, it simply cross-references the key with the table and retrieves the original information.

When used in a database, a hash system is used for efficiency and speed. These systems simplify large amounts of information down into smaller bits, a process that both saves space in the database and reduces the amount of time required to send information. For instance, the name John Smith may appear over and over again in a database. The hash system may represent that specific string of letters with the value '01.'

In the above example, John Smith consists of ten characters, with the space included, and 01 is only two. When the database goes for the information and the hash key 01 comes back, it will check its hash table and send out ‘John Smith.’ Since the hash key is only 20% of the actual value of the information, it saves space on every occurrence of the information; it also saves that much time in transmission.

Other systems will use a hash key to find redundant data. When a system contains huge amounts of data that need sorting for redundancies or patterns, it is often easier to hash the information rather than sort it by hand. Since different hashing algorithms collapse information in different ways, the data is generally sent through several hashing methods. When the hashing is complete, it is possible to find patterns very quickly using the resulting hash tables.

In the United States, this key is generally called the pound key, and the symbol is a pound sign or a number sign. In Canada, the key is often called a number key. Nearly the entire English-speaking world outside of North American calls it the hash key.

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M. McGee
By M. McGee
Mark McGee is a skilled writer and communicator who excels in crafting content that resonates with diverse audiences. With a background in communication-related fields, he brings strong organizational and interpersonal skills to his writing, ensuring that his work is both informative and engaging.
Discussion Comments
By anon1003625 — On Aug 03, 2020

This is the easiest definition and telling what is a hash key. Many websites describe a hash key like everyone knows what it is.

By anon1003186 — On May 17, 2020

Every other response to this article compares a hash key to a physical object, such as a key with "hash" symbol. But a hash key is a mathematical method for reducing the quantity of data processed, something like a numerical shorthand.

By Perdido — On Jun 07, 2012

@seag47 - I don’t know anything about assigning hash codes, either. I do have to use the hash key on my computer keyboard from time to time, though.

I call this key the “number” key. I type it before a number, and when someone reads the sentence, #1 reads “number one.”

I work for a newspaper, and we publish a section each year where people vote for the best businesses in the community. I am in charge of typing up the list of #1, #2, and #3 in each category, and I always use the hash key for this list.

By seag47 — On Jun 06, 2012

The only kind of hash key I’m familiar with is the one on my telephone’s keypad. I have to use it often when calling a place that has a recording.

Whenever I call my pharmacy to request a refill on a prescription, I am greeted with a recording that requires me to press a series of buttons. Once my order is complete, the recorded voice instructs me to press “pound,” or the hash key.

I have had to press this key when calling my credit card company before, also. Many companies like this make you press your way through a menu to get to the person you need to talk to, and often, the hash key is a part of this.

By lighth0se33 — On Jun 06, 2012

This sounds like a smart way to save time and stress on your fingers! I had no idea you could assign a hash value to something as long as a two-word name.

If I’m typing a document and I have a word or phrase that I need to repeat over and over, I just copy it and paste it wherever it is needed. I suppose this is just as efficient as using a hash key, but it’s nice to know that I have more than one option for doing shortcuts.

I type all day at my job, so I’m going to look into setting up some hash keys. This would be helpful when I have more than one phrase that I need to use often, since the copy and paste function can only remember one at a time.

M. McGee
M. McGee
Mark McGee is a skilled writer and communicator who excels in crafting content that resonates with diverse audiences....
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