sql basic

Question 1

SQL

Answer 1

Structured Query Language. It’s a standard language for managing and manipulating databases.

Question 2

creation of table in sql

Answer 2

create table ( ) ; – inside brackets we write data type with variable + primary constrain

Question 3

eg of creation of table

Answer 3

CREATE TABLE department (
Department varchar(100),
Division varchar(100),
PRIMARY KEY (Department)
);

Question 4

var char

Answer 4

that holds characters of variable length

Question 5

can we metion more than specified data in var char eg var(50) . Can we give 50+

Answer 5

yes

Question 6

eg of var char in creation of table

Answer 6

Department varchar(100), – column name (varchar – it can take data up to 100)

Question 7

Constrain

Answer 7

Constrain is a data base ability to control what kind of data need to go into the given column. This is data type specific.

Question 8

can we enter other data type after specified in the table

Answer 8

No

Question 9

Primary key

Answer 9

A primary key is a column or a set of columns that uniquely identify each row in the table. It must contain unique values and cannot contain null values.

Question 10

if we use primary key then we cant have duplicates

Answer 10

TRUE

Question 11

will primary key allow null

Answer 11

no

Question 12

How do you insert data into a table?

Answer 12

You can insert data into a table using the INSERT INTO

Question 13

eg of insert

Answer 13

INSERT INTO department (Department, Division(Column) ) VALUES (‘Automotive’, ‘Auto & Hardware’(values in column));

Question 14

how do we retrive all column from sql

Answer 14

SELECT *
FROM table_name;

Question 15

What is * in select * from table name ?

Answer 15

selecting all columns

Question 16

Retrival using column

Answer 16

SELECT column1, column2, …
FROM table_name;

Question 17

can we have mutiple primary key in creation of table

Answer 17

no

Question 18

statement in sql

Answer 18

();

Question 19

eg of statement

Answer 19

creation , insertion, Retrival of data

Question 20

can we mispell key words

Answer 20

no

Question 21

comment in sql

Answer 21

– single line comment /**/ multiline comment

Question 22

is ; manditory in selection statement

Answer 22

yes, but without that we can still continue

Question 23

date in sql

Answer 23

data type, ‘YYYY-MM-DD’

Question 24

row vs column

Answer 24

• |

Question 25

What is the WHERE clause in SQL?

Answer 25

The WHERE clause is used to filter records. It is case sensitive.

Question 26

What does the % symbol do in a WHERE clause?

Answer 26

The % symbol is a wildcard character that represents zero, one, or multiple characters in a LIKE condition.

Question 27

What is the LIKE operator in SQL?

Answer 27

used in a WHERE clause to search for a specified pattern in a column.

Question 28

What does the error “UNIQUE constraint failed: Customers.customer_id” mean?

Answer 28

This error means that an attempt was made to insert a duplicate value into a column that has a UNIQUE constraint.

Question 29

What is a FOREIGN KEY in SQL?

Answer 29

a field (or collection of fields) in one table that refers to the PRIMARY KEY in another table.

Question 30

How do you update data in a table?

Answer 30

You can update data in a table using the UPDATE statement.

Question 31

eg of update table ?

Answer 31

UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;

Question 32

How do you delete data from a table?

Answer 32

You can delete data from a table using the DELETE statement.

Question 33

example of delete data

Answer 33

DELETE FROM table_name WHERE condition;

Question 34

can we have multiple condition in where clause?

Answer 34

yes we can use and , or

Question 35

AND

Answer 35

if we mention this then it must be true

Question 36

OR

Answer 36

If we are not sure then we can use this

Question 37

can we have and , or at same time

Answer 37

yes and (or)

Question 38

NOT

Answer 38

this gives opposite of required

Question 39

Not Types

Answer 39

NOT | <> | !=

Question 40

What is NULL in SQL?

Answer 40

NULL represents missing or unknown data in SQL. It is not the same as zero or an empty string.

Question 41

if we want null value

Answer 41

where column is null

Question 42

if we don’t want null values

Answer 42

where column is not null

Question 43

how can we write multiple condition like where and or or or or in same column

Answer 43

IN can be used

Question 44

if you want to search between the range

Answer 44

BETWEEN

Question 45

how can we arrage column in ascending or decending

Answer 45

ORDER BY column name or ORDER BY 1 (By default its acending) her 1 means true

Question 46

for ascending using order by

Answer 46

ORDER BY column name or ORDER BY column name ASC

Question 47

for decending using order by

Answer 47

ORDER BY column name DESC

Question 48

where we write order by

Answer 48

we must write at last of query

Question 49

if we don’t want duplicates to print

Answer 49

distinct

Question 50

if you want to print first 10

Answer 50

LIMIT 10 or Fetch first 10 rows only

Question 51

can we fetch last rows

Answer 51

NO we cant

Question 52

How Rename a column

Answer 52

AS

Question 53

TYPES of AS

Answer 53

column_name or "COLUMN Name"

Question 54

example of as

Answer 54

SELECT column_name AS new_column_name.

Question 55

how to make all column data caps

Answer 55

UPPER(Column Name)

Question 56

how to make all column data lower case

Answer 56

lower(Column Name)

Question 57

TO know the length of string (akil - 4)

Answer 57

LENGTH(Column name)

Question 58

Do length calculate the space

Answer 58

yes

Question 59

how to add string data in sql

Answer 59

Select ' what ever string u can write here '

Question 60

what is white space

Answer 60

the excess gap between string

Question 61

how do we eliminate white spaces

Answer 61

The TRIM() function removes leading and trailing spaces from a string.

Question 62

example of trim

Answer 62

Select TRIM ( ' what ever string u can write here ' ). >> what ever string u can write here (no whitespaces)

Question 63

How do we add 2 columns

Answer 63

PIPES || ' ' || where ' ' will add spaces between (column1 || ' ' || column2)

Question 64

PIPes also called as

Answer 64

CONCAT

Question 65

to check condition true or false

Answer 65

BooLean ( ) - we specify column in the brackets

Question 66

Data checking in columns

Answer 66

Select column ,(‘data in column’ IN (column name, column name))

Question 67

Data checking using string

Answer 67

Select column ,(‘data in column’ IN ('data in column ','data in column ','data in column '))

Question 68

Print of sub string by specifing star and end point

Answer 68

(SELECT SUBSTRING('Akhil is present', Start point, End Point);)

Question 69

Print of sub string from start point only

Answer 69

(SELECT SUBSTRING('Akhil is present' from 3 ); o/p - il is present

Question 70

to replace string

Answer 70

Replace (column , ‘existing data’ , ‘new data that replays’ )

Question 71

to know the position of the word or symbol

Answer 71

The POSITION() function returns the position of the first occurrence of a substring in a string.

Question 72

example of position

Answer 72

Eg abc@gmail.com then @ is at 4th position.

Question 73

if you don’t want to print the position specified

Answer 73

use +1

Question 74

Replace null with data

Answer 74

Coalesce ( column , 'Data that you want to replace' ):

Question 75

Single row function

Answer 75

4 rows input we get 4 rows output (allow duplicates)

Question 76

How do you check if a column contains a specific word in SQL?

Answer 76

You can use the LIKE operator with % wildcard characters. For example, WHERE column_name LIKE '%word%'.