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DBMS Class 2

DBMS Normalization Rest

June 22, 2023

Composite primary key- data is not identified by one pk, so another key needed, that pk is compost key.

Column/attribute ||

Row=

who is dependent on who

Prime attribute: when dependent on PK is Prime attribute.

Transitive Attribute: dependency non k on non key

Normalization- একটা টেবিল ভেঙ্গে চারটা

Step 3 - অনুযায়ী আলাদা হল।

1st, 2nd and 3rd Normalization যদি পারা যায় তাহলে ডাটাবেজের কাজ আরামে করতে পারবেন।

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Question for Exam

What is data?> piece of info

What is Record/Information? > collection of related data.

What is Table?> Collection of related record.

What is DB?> Collection of table

What is DBMS> software এর মাধ্যমে ..

Example?>

RDBMS: Relational DBMS​

SQL> Structured Query Language

Relational Database Management System (RDBMS) consists of A set of related tables

A schema

A schema: A database schema is the skeleton structure that represents the logical view of the entire data.

Tables/relations:

Stores information about an entity or theme-Consist of columns (fields) and rows (records).

Rows /tuples, describing information about a single item, ie A specific student

columns /attributes, describing a single characteristic (attributes) of its item. ie id, name, address etc

Every row is unique & identified by a key

(Sample of RDBMS)

একই টেবিলে দুইটা ফরেন কি থাকতে পারে

Data types in MYSQL

MySQL uses many different data types broken into three main categories -

  • Numeric
  • Date and Time
  • String Types.

Numeric Data Types​

The following list shows the common numeric data types and their descriptions -

  • INT-A normal-sized integer that can be signed or unsigned. If signed, the allowable range is from -2147483648 to 2147483647. If unsigned, the allowable range is from 0 to 4294967295. You can specify a width of up to 11 digits.

(Not important, int used mostly)

  • TINYINT A very small integer that can be signed or unsigned. If signed, the allowable range is from -128 to 127. If unsigned, the allowable range is from 0 to 255. You can specify a width of up to 4 digits.
  • SMALLINT - A small Integer that can be signed or unsigned. If signed, the allowable range is from -32768 to 32767. If unsigned, the allowable range is from 0 to 65535. You can specify a width of up to 5 digits.
  • MEDIUMINT - A medium-sized integer that can be signed or unsigned. If signed, the allowable range is from -8388608 to 8388607. If unsigned, the allowable range is from 0 to 16777215. You can specify a width of up to 9 digits.
  • BIGINT A large integer that can be signed or unsigned. If signed, the allowable range is from -9223372036854775808 to 9223372036854775807. If unsigned, the allowable range is from 0 to 18446744073709551615. You can specify a width of up to 20 digits.
  • FLOAT(M,D)- A floating-point number that cannot be unsigned. You can define the display length (M) and the number of decimals (D). This is not required and will default to 10,2, where 2 is the number of decimals and 10 is the total number of digits (including decimals). Decimal precision can go to 24 places for a FLOAT.
  • DOUBLE(M,D)- A double precision floating-point number that cannot be unsigned. You can define the display length (M) and the number of decimals (D). This is not required and will default to 16,4, where 4 is the number of decimals. Decimal precision can go to 53 places for a DOUBLE. REAL is a synonym for DOUBLE.

Among these Int, Big Int, Double and Float needed.

Date handle করা সবচে Difficult.