# [25/4/2023] Tech practices (SQL)

### Q1
Which is the correct order in an SQL SELECT statement?

- [ ] SELECT, FROM, WHERE, GROUP BY, ORDER BY, HAVING
- [ ] SELECT, FROM, GROUP BY, HAVING, WHERE, ORDER BY
- [x] SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY
- [ ] SELECT, FROM, GROUP BY, HAVING, ORDER BY, WHERE

### Q2
What is a view?

- [ ] A view is a special stored procedure executed when certain event accurs
- [x] A view is a virtual table which results of executing a pre-compiled query.A view is not part of the physical database schema, while the regular tables are.
- [ ] A view is a database diagram
- [ ] None of these

### Q3
Which of the following are SQL aggregate functions?

- [ ] JOIN
- [x] AVG
- [ ] LEN
- [x] SUM

### Q4
Which is the result of SQL statement `SELECT SUBSTR('123456789', INSTR('abcabcabc', 'b'), 4) AS extractStr;`?

- [ ] 6789
- [x] 2345
- [ ] 1234
- [ ] 456789

### Q5

Which of the following functions ignore NULL values?

- [ ] MAX
- [ ] COUNT
- [ ] SUM
- [x] All of these

### Q6

What is the meaning of LIKE 'r_%'

- [ ] String begins `r_`
- [ ] String ends with `r_`
- [x] String begins with `r` and at least 2 characters in length
- [ ] String has substring `r_` int it, at any position

### Q7

Which of the following join is also called as an **inner-join**?

- [ ] Non-Equijoin
- [ ] Self-Join
- [x] Equijoin
- [ ] None of these

### Q8
Which of the following is a type of SQL constraint?

- [x] PRIMARY KEY
- [ ] ALTERNATE KEY
- [x] FOREIGN KEY
- [x] UNIQUE

### Q9
What SQL command can be used to delete a column from a table?

- [ ] MODIFY TABLE tableName DROP columnName;
- [ ] MODIFY TABLE tableName DROP COLUMN columnName;
- [ ] ALTER TABLE tableName DROP columnName;
- [x] ALTER TABLE tableName DROP COLUMN columnName;

### Q10
Table **employee** has 10 records. It has a non-NULL **salary** column which is also UNIQUE. Which is the result of the SQL statement `SELECT COUNT(*) FROM employee WHERE salary > ANY (SELECT salary FROM EMPLOYEE)`?

- [ ] 10
- [x] 9
- [ ] 5
- [ ] 0