Below is a complete, academic-quality description of the ER (Entity–Relationship) Model in DBMS, written in clear language and suitable for projects, internship reports, exams, and assignments. Length is approximately 3000 words. You may use it directly. ⸻ ER Model in DBMS – Detailed Description 1. Introduction A Database Management System (DBMS) is software that allows users to define, create, store, retrieve, and manage data efficiently. In modern applications, databases are used in almost every field, including banking, education, healthcare, e-commerce, transportation, and social media. To design a database that accurately represents real-world data and relationships, a proper data modeling technique is required. The Entity–Relationship (ER) Model is one of the most widely used conceptual data models in DBMS. It was introduced by Peter Chen in 1976 and provides a high-level, graphical approach to database design. The ER model helps database designers visualize data structures, relationships, and constraints before implementing the database in a relational or other database model. The ER model plays a crucial role in bridging the gap between real-world scenarios and database structures. It simplifies complex systems into understandable components and ensures accurate database design. ⸻ 2. Definition of ER Model The ER Model is a conceptual data model that represents data in the form of entities, attributes, and relationships. It focuses on describing the structure of data rather than the physical storage of data. • Entity represents a real-world object. • Attribute describes the properties of an entity. • Relationship represents the association between entities. The ER model is mainly used during the database design phase, especially in the early stages, to understand requirements clearly. ⸻ 3. Purpose of ER Model The main purpose of the ER model is to: 1. Provide a clear conceptual design of the database 2. Represent real-world objects and their relationships 3. Reduce complexity in database design 4. Improve communication between users, analysts, and developers 5. Ensure data accuracy and consistency By using the ER model, database designers can avoid redundancy, anomalies, and structural errors in the final database. ⸻ 4. Components of ER Model The ER model consists of several basic components that together describe the database structure. ⸻ 5. Entity 5.1 Definition of Entity An entity is a real-world object or concept that can be uniquely identified and has an independent existence. Entities can be physical or abstract. Examples: • Student • Employee • Customer • Course • Product 5.2 Types of Entities 5.2.1 Strong Entity A strong entity has its own primary key and does not depend on any other entity for identification. Example: Student (Student_ID, Name, Age) 5.2.2 Weak Entity A weak entity does not have a primary key of its own and depends

1. SQL- Operators and
Functions
HKPATEL

2. HKPATEL 2
DUAL & SYSDATE
• DUAL
– It is a table having
one row & One
Column
– Oracle created by
itself
– Select * from Dual;
– Select 5*5 from Dual;
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D
X
5*5
25
• SYSDATE
– It contain the current
date and time
– Select sysdate from
Dual; SYSDATE
20-jun-17

3. HKPATEL 3
Operators
• Arithmetic
– +, -, *, /,()
• Relational
– <, >, <=, >=, +, !== or <>,
• Logical
– AND, OR, NOT
• Range searching
• Set searching
• Character
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4. HKPATEL 4
Range Searching Operator-
BETWEEN
• Syntax
– Column_name BETWEEN lower limit and upper limit;
• Ex.
– Select* from EMP where sal BETWEEN 500 and 1500;
• Add NOT in this Operator
– Select* from EMP where sal NOT BETWEEN 500 and
1500;
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5. HKPATEL 5
Set Searching Operator - IN
• Syntax
– Column_Name IN (val1, val2,…,valN);
• EX.
– Select * from emp where city IN(‘vvn’,
‘and’, ‘ahm’);
• Add NOT in this Operator
• Select * from emp where city NOT
IN(‘vvn’, ‘and’, ‘ahm’);
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6. HKPATEL 6
Character Operators – LIKE
• LIKE
– Syntax
• Col_name like pattern
– Pattern can be formed by using 2 wild card character
– % (Modulo) allow matching with any string having no. of
char.
– _ (Under score) allow matching with single charcater.
– EX.
– Display emp having city name starting with A
• Select * from emp where city like ‘A%’
– Display emp whose name have second character a
• Select * from emp where city like ‘_a%’
• _
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7. HKPATEL 7
Character Operators – ||
• Concatenates (combine two string)
• Syntax
– String1 || string2
• Ex.
– Select ename||city from emp;
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8. HKPATEL 8
SQL Functions
• Aggregate Functions
• Scalar Functions
– Numeric
– Character
– Date
– Conversion
– Miscalleous
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9. HKPATEL 9
Aggregate Functions
• Max (colname)
• Min (colName)
• Sum([Distinct|all] colName)
• Avg([Distinct|all] colName)
• Count (*)
• Count([Distinct|all] colName)
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10. HKPATEL 10
Numeric Functions
• ABS – Abs(n)- convert n to +ve
• SQRT – sqrt(n) - returns square root of n
• POWER- power(m,n)- returns m raised to n
• MOD- mod(m,n)- Remainders of m divide by n
• CEIL-ceil(n)- return largest int value
• FLOOR- floor(n)- return Smallest int value
• EXP-exp(n)- e raised to n
• LN-ln(n)- log n to the base e.
• LOG- log(b,n)- log n to the base b
• COS, SIN & TAN- cos(n), sin(n) & Tan(n)
• COSH, SINH & TANH- cosh(n), sinh(n) & Tanh(n)
• SIGN- sign(n)-return sign of n
• ROUND
• TRUNC
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11. HKPATEL 11
• Round
– Round(m,n)
• Return m, rounded to n places
• If n is omited, m is rounded to zero places
• If n is negetive, m is rounded to n places to the left
• If n is positive, m is rounded to n places to the left
DBMS-3330703-2017
Select round(157.732,2), round(157.732,-2), round(157.732) from dual;
157.73 200 158
• Trunc
– trunc(m,n)
• Return m, rounded to n places
• If n is omited, m is truncated to zero places
• If n is negetive, m is rounded to n places to the left
• If n is positive, m is truncated to n places to the left
Select trunc(157.732,2), trunc(157.732,-2), trunc(157.732) from dual;
157.73 100 157

12. HKPATEL 12
Character functions
• Length(str)
• Lower(str)
• Upper(str)
• Initcap(str)
• Ascii(char)
• Lpad(str,n,str2)
– Rerurn str, left padded with str2 up to length n
– lpad(‘ind’,5,’*’)- **ind
• Rpad (str,n,str2)
– Rerurn str, right padded with str2 up to length
n
– - rpad(‘ind’,5,’*’)- ind**
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13. HKPATEL 13
Character functions
• Ltrim (str,set)
– Removes the character from the left to str
– ltrim(‘abhkp’, ‘baaks’) - hkp
• Rtrim (str,set)
– Removes the character from the right to str
– rtrim(‘abhkp’, ‘pkhs’) - ab
• Translate (str, from_set, to_set)
• Replace (str, from_set, to_set)
• Substr (str,pos,length)
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14. HKPATEL 14
Translate V/S Replace
• Translate(str, from_set, to_set)
– Character of str that occur in from_set are
translated to the corresponding char in to_set.
– Translate(‘abc12efg3’,’1234’,xyzw)
– abcxyefgz
• Replace (str, from_set, to_set)
– Replace to similar translate but it works on
string rathar than character
– Replace (‘abc12efg3’,’1234’,xyzw)
– Abcxyzefg
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15. HKPATEL 15
SUBSTRING
• Substr(str,pos,length)
• Returns a portion of str, beginning at pos and
going up to length charcters
• SUBSTR(‘KARM HARDIK PATEL’,6,4)
– HARD
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16. HKPATEL 16
Conversion functions
• To_NUMBER( str)
– convert value of character data type ,expressing a
number to number data type
• TO_CHAR(n, format)
– convert numeric value n to a character data type
using optional format.
• TO_CHAR( date, format)
– converting date value to character value using format.
• TO_DATE( str, format)
– converts character value to date value
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17. HKPATEL 17
Date Functions
• Add_months (date1, n)
– Return new date after adding n months in date1
• Months_between(date1, date2)
– Return number of months between date1 and date2.
– Date1-Date2
• Last_Day (date1)
– Returns the last date of the month specified by date1
• Next_Day(day, date1)
– Return the next named week-day specified by day to relative
date1.
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18. HKPATEL 18
Continue
• Round (date, format)
– Returns rounded date according to format
– Select(TO_DATE(‘31-DEC-18 03:30:45PM’,’DD_MON_YY
HH:MM:SS PM’))from dual;
– O/P: 01-JAN-19
• Trunc (date, format)
– Returns truncated date according to format
– Select(TO_DATE(‘31-DEC-18 03:30:45PM’,’DD_MON_YY
HH:MM:SS PM’))from dual;
– O/P: 31-DEC-18
• New_Time(date,Zone1,Zone2)
– Returns the date after converting it from time zone 1 to time zone
2
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19. HKPATEL 19
Miscellaneous Function
• UID
– Returns the uid of the current user
• USER
– Returns the user name
• GREATEST(exp1,exp2,exp3)
– Returns the greatest exp
• LEAST(exp1,exp2,exp3)
– Returns the least exp
• DECODE(Value,if1,then1,if2,then2,…,else)
– It similar if-then-else
• NVL(exp1,exp2)
– Returns exp2, if exp1 is null--Returns exp1, if it is not null
• VSIZE(exp)
– Retuns the storage size of exp in oracle
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20. HKPATEL 20
Thank You
DBMS-3330703-2017