chapter 1

Question 1

what does APEX enable users to do

Answer 1

Enables users to build and access applications as if they were running in separate databases.

Question 2

what are the 2 components of apex

Answer 2

–> SQL workshop (learn sql)
–> application builder (design applcation)

Question 3

which command is used to return all the rows in table

Answer 3

SELECT *

Question 4

what is the syntax for select statement

Answer 4

SELECT *
FROM <TABLE_NAME>;</TABLE_NAME>

Question 5

a statement is a ______

Answer 5

COMBINATION OF 2 OR MORE CLAUSES

Question 6

what does the from clause specify

Answer 6

specifies the table containing the columns listed in the select clause

Question 7

what statement do you use if you want to return a subset of the data

Answer 7

WHERE <CONDITION_1>;</CONDITION_1>

Question 8

when will you get the invalid SQL statement error

Answer 8

incorrect spelling for sql commands

Question 9

When will you get the Name invalid identifier error

Answer 9

when you enter the incorrect column name

Question 10

when will you get the invalid SQL statement error

Answer 10

incorrect spelling for SQL commands

Question 11

what is a relational database table

Answer 11

–> It is a collection of objects or relations, a set of operators to act on those relations, and data integrity for accuracy and consistency.

–> allows tables to be related by a common field

Question 12

what percentage of the world’s data resides in rdbms

Answer 12

20%

Question 13

which companies use RDBMS

Answer 13

amazon.com
France telecom
The Claria corporation

Question 14

what is a field

Answer 14

one value found at the intersection of a row and column.

Question 15

what is a column

Answer 15

one kind of data in a table

Question 16

what is a table

Answer 16

basic storage structure

Question 17

what is a row

Answer 17

data for one table instance

Question 18

what is primary key

Answer 18

unique identifier for each row

Question 19

what is a foreign key

Answer 19

column that refers to the primary key column in another table

Question 20

what are the 6 table properties?

Answer 20

–> Entries in columns are single-valued
–> Entries in columns are of the same kind
–> Each row is unique
–> sequence of columns is insignificant
–> sequence of rows is insignificant
–> Each column has a unique name

Question 21

_______ organizes data into related rows and columns

Answer 21

Relational database management system

Question 22

what do you use to access the data in rdbms

Answer 22

SQL statements and operators

Question 23

in a very large database system ____, _____, and ______ make up the RDBMS

Answer 23

many users, servers and tables

Question 24

what are the 4 categories of sql statements

Answer 24

–> data manipulation language (DML)
–> data definition language (DDL)
–> Transaction control language (TCL)
–> data control language (DCL)

Question 25

what is DML

Answer 25

–> used to modify the table data by entering new rows, changing existing rows, or removing existing rows.

–> eg: Insert, Update, Delete, Merge

Question 26

which category of Sql statements does select come under

Answer 26

It is a limited form of DML in that it can only access the data in the database. It cannot manipulate the data in the database, although it can operate on the accessed data before returning the results of the query

Question 27

what is DDL

Answer 27

–> DDL statements create, change and remove the data structures from the database

–> eg: create, alter, drop, rename, and truncate begin DDL statements

Question 28

what is transaction control language (TCL)

Answer 28

–> used to manage the changes made by DML statements
–> can be grouped together into logical statements
–> eg: commit, rollback and savepoint

Question 29

what is the data control language (DCL)

Answer 29

–> give or remove access rights to the database
–> eg: Grant, revoke

Question 30

what must a select statement include

Answer 30

–> select clause
–> from clause

Question 31

what are the capabilities of select statements

Answer 31

–> projection: used to choose columns in a table that you want to be returned by your query
–> selection: used to choose rows in a table that you want returned by your query

Question 32

which clause determines selection

Answer 32

WHERE clause

Question 33

which clause determines projection

Answer 33

SELECT clause

Question 34

what is precedence in arithmetic operators

Answer 34

it is the order in which sql evaluates the arithmetic operators

Question 35

what is order of arithmetic operators

Answer 35

• / + -
  (My Dear Aunt Sally)

Question 36

what happens when the operators are of the same priority

Answer 36

evaluation is done from left to right

Question 37

_______ is not the same as a 0 or space

Answer 37

Null

Question 38

why use NULL

Answer 38

When you dont know the value for a column, you cannot store unknowns in your database. Relational databases use a placeholder called NULL to represent these unknown values

Question 39

what happens when you try to divide by null

Answer 39

result is null or unknown

Question 40

how are null values displayed in apex

Answer 40

by a dash (-)

Question 41

what is an alias

Answer 41

way of renaming a column heading in the output. It is used to display a name which is easier to understand and is more user friendly

Question 42

what are the column alias rules

Answer 42

–> renames a column heading
–> is useful with calculations
–> Immediately follows the column names
–> May have optional AS keyword between the column name and alias
–> Requires double quotation marks if the alias contains special characters or is case sensitive

Question 43

is this valid

SELECT last_name AS lname
from students;

Answer 43

Yes, as quotation marks are not needed when using the as keyword. Also the column name LNAME will be displayed in caps