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38 changes: 30 additions & 8 deletions 2-classes-db/task.md
Original file line number Diff line number Diff line change
Expand Up @@ -21,27 +21,46 @@ To submit this homework write the correct commands after each question.

### 1. Show the date, transaction_no, description and amount for those transactions whose amount is between £30,000 and £31,000.
```sql

SELECT date, transaction_no, description amount
FROM spends
WHERE amount > 30,000 AND < 31000;
```
### 2. Show the date, transaction_no, supplier_inv_no, description and amount for those transactions whose description includes the word 'fee'.
```sql

SELECT date transaction_no, supplier_inv_no,
description, amount
FROM
spends
WHERE
description LIKE '%fee%';
```
### 3. Show the date, transaction_no, supplier_inv_no, description and amount for those transactions whose description includes the word 'Fee'.
```sql

SELECT date, transaction_no, supplier_inv_no,
description, amount
FROM
spends
WHERE
description LIKE '%Fee%';
```
### 4. Show the date, transaction_no, supplier_inv_no, description and amount for those transactions whose description includes the word 'fee' (case insensitive). You will need to search 'https://www.postgresql.org/docs/' to solve this.
```sql

SELECT date, transaction_no, supplier_inv_no, description, amount
FROM spends
WHERE LOWER(description) LIKE LOWER('%Fee%');
```
### 5. Show the date, transaction_no, supplier_inv_no, description and amount for those transactions whose amount is £25,000, £30,000, £35,000 or £40,000.
```sql

SELECT date, transaction_no, supplier_inv_no, description, amount
FROM spends
WHERE amount IN (25000, 30000, 35000, 40000);
```
### 6. Show the date, the supplier_id, the description and the amount for transactions with the expense area of 'Better Hospital Food'. You could do a query to get the expense_area_id first then do a query to find the dates, supplier_ids and amounts. But it would be better to do this all in one query by linking the tables together using INNER JOINs.
```sql

SELECT date, supplier_id, description, amount FROM spends
INNER JOIN expense_areas
ON expense_areas.id = spends.expense_area_id
WHERE expense_areas.expense_area = 'Better Hospital Food';
```
### 7. Show the date, supplier name, description and amount for transactions with the expense area of 'Better Hospital Food'. You will need to INNER JOIN another table to be able to do this.
```sql
Expand All @@ -56,11 +75,14 @@ To submit this homework write the correct commands after each question.
the expense area is 'ICT Contingency' (id 18)
for £32,000.
```sql

INSERT INTO spends(date, description, transaction_no, supplier_inv_no, supplier_id, expense_type_id, expense_area_id, amount)
VALUES('2021-04-01','Computer Hardware Dell',38104091,'3780119655', 16, 7, 18, 777);
```
### 9. If you examine the dates in the data, you will see they all are dated either 1st march 2021 or 1st April 2021. So if we group on the the date, there will only be two groups. Show the date and the total amount spent on that date for these two dates by using a GROUP BY clause.
```sql

SELECT date, SUM(amount) AS total_amount
FROM spends
GROUP BY date;
```
### 10. (optional) Great we now know the monthly spend. But it didn't look that good. So I've changed my SELECT query to output this instead:
```
Expand Down