Advantages of a Database
Schools managed for a century with paper registers, and plenty of small offices still do. So this is a fair question, and it is one both syllabuses ask by name: what does a database actually give you that a shelf of registers does not?
1Start with the problem
A school keeps a fee register, a library register and a transport register. Ravi appears in all three, and so does his address. Then Ravi moves house.
His address is on file in three places. Correct it and see what happens to the other two.
Three registers, three copies of one fact. Update just one of them — as a busy clerk would.
That is the whole argument in one picture. The trouble with three copies is not the paper they use — it is that correcting one of them makes it disagree with the other two, and nothing in the building can say which is right.
21 · Controlled redundancy, and the consistency it buys
Redundancy means the same fact stored more than once. A database does not forbid it outright — sometimes a little is useful — but it lets you control it: store the address once, in one table, and let everything else refer to it.
Consistency follows automatically. Data is inconsistent when two copies of one fact disagree. Remove the second copy and there is nothing left to disagree with.
32 · Data sharing
One register can be on one desk. A database can be used by the office, the librarian and the exam cell at the same time, each seeing the same up-to-date data. The DBMS handles what happens when two people change the same record at the same moment — something a paper register simply cannot do.
43 · Data integrity
Integrity means the data obeys the rules that make it sensible. You write those rules once and the database enforces them on every row, for every user, for ever — no roll number twice, no nameless student, no age of 250.
Rules like these are not left to people remembering them. They are written into the table at the moment it is built, and the database then refuses any row that breaks one. Writing them is a lesson of its own — Constraints, in the coming chapters.
54 · Data security
A register on a desk shows everything to whoever opens it. A database can give each person their own username and password, and let them see only what they need — the librarian gets names and book issues, not marks or fees. Access is granted per user, and can be taken away again.
65 · Backup, recovery — and finding things
A copy can be taken every night and restored after a crash. A register that is lost, burnt or soaked is simply gone, and so is every year it covered.
“Every class 12 student above 78% from Gangtok” is one instruction, answered in a moment. By hand it means reading every page and keeping a tally.
That second one is worth pausing on, because it is the advantage you will feel most in this course. The entire Querying with SELECT chapter exists because asking a precise question of a large pile of data is easy for a database and miserable for a person.
7All of them together
| Registers / separate files | A database with a DBMS | |
|---|---|---|
| The same fact | Copied into every register that needs it | Stored once, referred to from anywhere |
| After a correction | The copies disagree until every one is found | There is only one copy, so it is simply right |
| Two people at once | One desk, one register, one person | Many users at the same time |
| Rules about the data | Whatever people remember to follow | Enforced by the database on every row |
| Who can see what | Whoever opens it sees everything | Granted per user, and revocable |
| If it is lost | Gone | Restored from a backup |
| Finding one thing | Read every page | One query |
8And what it costs
An honest answer names the price too, and questions sometimes ask for it:
Software, a machine to run it on, and often someone paid to look after it.
Designing the tables well takes skill. A badly designed database can be worse than a register.
If the server goes down, everyone stops — which is exactly why backups matter.
For a shopkeeper with twenty customers, a notebook still wins. For a school with a thousand students, or a bank, the advantages stop being conveniences and become the only workable option.
9Recap
Store a fact once instead of in every register.
Follows from the above — no second copy to disagree.
Many users at the same time, on the same data.
Rules enforced by the database, not by memory.
Each user sees only what they are granted.
Restorable after a crash; one query instead of a search.
A school stores each student's address in three separate registers. Which problem is this most likely to cause?
Data consistency is best described as…
Which advantage means the librarian can see names but not marks?
Which of these is a genuine disadvantage of using a DBMS?