Clauses are used to define any specific condition with the commands like select, insert, update, delete, alter.
Table of Contents
WHERE CLAUSE IN SQLITE :
Where clause is used to filter out the result, for that define a condition with where clause.If the specified condition is true it return the records. It is used with update, select, alter..etc.
Syntax
select column1, column2, columnN from where <condition>;
Usage:
sqlite> select * from t1; Number Name --- --- 101 Ram 102 Ram Kumar 103 Krishan 104 Ramesh sqlite> select name from t1 where num=102; Name ---- Ram Kumar sqlite>
AND/ OR Clause
These clause is used to retrieve records or you can say multiple records with the specified condition define which these two clauses.
AND :
With ‘AND’ clause we can define multiple conditions but it turns true if all specified conditions with it stands true. Like we define a [condition1] and [condition2], will be true if both are condition1 , condition2 are true.
Syntax
Where [condition1] AND [condition2] AND [condition3] ... AND [conditionN]
Example: EMPLOYEE TABLE
Eno Ename Esalary Eaddress --- ----- ------- ------ 101 Rajat 50000.0 Karnal 102 Ranjit 56000.0 Karnal 103 Rahul 66000.0 Karnal 104 Ravi 66000.0 Kaithal 105 Ravina 75000.0 Kaithal
Usage:
sqlite> select Eno from Employee where Eaddress='Karnal'; Eno --- 101 102 103
OR:
With ‘OR’ clause we can define multiple conditions but it returns true if any specified conditions with it is true. Like we define a [condition1] and [condition2], will be true if any of the condition either condition1 , condition2 is true.
Syntax
Where [condition1] AND [condition2] OR [condition3] ... OR [conditionN]
Usage:
sqlite> select Eno, Ename from Employee where Eaddress='Karnal' or Esalary=75000; Eno Ename --- ----- 101 Rajat 102 Ranjit 103 Rahul 105 Ravina
LIKE CLAUSE
Like clause is used to match values using wildcards. The wildcards are the special character which have some meaning for it.
— Percentage “%” – This represents one or more characters.
— Underscore “_” – This represents single character.
Usage:
In following example will return records with Ename ending with alphabet ‘t’.
sqlite> select Esalary from Employee where ename like '%t'; Esalary ------ 50000.0 56000.0
In following will return records as starting with ‘R’ followed by any letter after that ‘v’ than any number of letters.
sqlite> select Eno ,Ename from Employee where Ename like 'R_v%'; Eno Ename --- ---- 104 Ravi 105 Ravina
GLOB CLAUSE
Glob clause is used to match text values against pattern using unix wildcards. Glob clause is case_ sensitive unlike like clause. The wildcards are the special character which have some meaning for it.
— Asterisk “*” – This represents one or more characters.
— QuestionMark “?” – This represents single character.
Usage:
In following example will return records with Ename ending with alphabet ‘t’.
sqlite> select Esalary from Employee where ename glob '*t'; Esalary ------ 50000.0 56000.0
In following will return records as starting with ‘R’ followed by any letter after that ‘v’ than any number of letters.
sqlite> select Eno ,Ename from Employee where Ename glob 'R?v*'; Eno Ename --- ---- 104 Ravi 105 Ravina
Important Note: The basic difference between Like and Glob is that Glob is case-sensitive but like operator is not further Glob uses unix wildcards.
LIMIT & OFFSET CLAUSE
In SQLite limit clause basically limits the output, it only display as much rows as defined in it, let’s see the example.
Usage:
In the below example if you see the limit is set to “3”, then it will display first 3 records.
sqlite> select * from Employee limit 3 ; Eno Ename Esalary Eaddress --- ----- ------- ------- 101 Rajat 50000.0 Karnal 102 Ranjit 56000.0 Karnal 103 Rahul 66000.0 Karnal
OFFSET CLAUSE
Using Offset with Limit clause will set a offset that after the defined offset the records will display.
Usage:
In the below query the limit clause will display 2 records as explained above and the offset will leave defined number of records in it.
sqlite> select * from employee limit 2 offset 2; Eno Ename Esalary Eaddress --- ----- ------- -------- 103 Rahul 66000.0 Karnal 104 Ravi 66000.0 Kaithal
ORDER BY CLAUSE
Order By Clause as the name symbolized it sorts the data is specified order i.e either ascending or descending. By default the order is ascending. You can use multiple columns with order by clause.
Usage:
In the below example order by clause is used which is ordering the records by Eaddress.
sqlite> select Ename, Esalary from employee order by Eaddress ASC; Ename Esalary ----- ------- Ravi 66000.0 Ravina 75000.0 Rajat 50000.0 Ranjit 56000.0 Rahul 66000.0
In below example we used order by clause which is sorting records in descending order.
sqlite> select Ename, Esalary from employee order by Eaddress DESC; Ename Esalary ----- ------- Rajat 50000.0 Ranjit 56000.0 Rahul 66000.0 Ravi 66000.0 Ravina 75000.0
GROUP BY
Group By Clause is used to group put the similar records together. This clause is used with the select query and optionally you can use order by clause with it.
Usage:
In the below example we want to know the no of employees from same location. So we used group by with count function, further we add order by clause which is sorting records according to Eno.
sqlite> select Eaddress, count(Eaddress) as Number_of_Employees from employee group by Eaddress order by Eno; Eaddress Number_of_Employees ------- ------------------- Karnal 3 Kaithal 2
HAVING CLAUSE
Having clause is used to specify a condition with the group by.
Usage:
In the following example we just count the no of employees from kaithal by grouping them.
sqlite> select Eaddress, count(Eaddress) as Number_of_Employees from employee group by Eaddress having Eaddress='Kaithal'; Eaddress Number_of_Employees -------- ------------------- Kaithal 2
DISTINCT / ALL
Distinct as itself explains it display unique data.
Usage:
In below query distinct address records are fetched.
sqlite> select Distinct Eaddress from employee; Eaddress ------ Karnal Kaithal
Similarly using ALL, will display all records:
sqlite> select All Eaddress from employee; Eaddress -------- Karnal Karnal Karnal Kaithal Kaithal
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