Adds sub-queries and functions.

database/notes/07-subqueries-functions-worksheet.md

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+# Queries
+
+## Sub-queries
+
+1. Get all the students whose IQ is greater than the average IQ.
+
+```sql
+
+```
+
+2. Get all the students whose IQ is greater than the highest IQ of the batch_id `2` students.
+
+```sql
+
+```
+
+3. Get all the students whose IQ is greater than `all` the IQs of the batch_id `2` students.
+
+```sql
+
+```
+
+4. Find all the students who are in batches that start with the word `Jedi` (Without JOIN)
+
+```sql
+
+```
+
+5. Find all the students whose IQ is greater than the average IQ of their batch.
+
+```sql
+
+```
+
+6. Get all the instructors that have at least one batch (Without using joins)
+
+```sql
+
+```
+
+7. Print all the names, batch ID and average IQ of the batch for each student
+
+```sql
+
+```
+
+## Built-in Functions
+1. Get the average IQ of all the students rounded to the nearest integer.
+
+```sql
+
+```
+2. Find all batches whose name is longer than 10 characters.
+
+```sql
+
+```
+
+3. Find all batches whose name's first 10 characters contains the string `sher`
+
+```sql
+
+```
+
+4. Get all batches that have started on a Sunday
+
+```sql
+
+```
+
+5. Get all batches that have been running for more than 10 years
+
+```sql
+
+```
+6. Print the name and the instructor's id for each batch. If no instructor is assigned, print `NO INSTRUCTOR`.
+
+```sql
+
+```
+
+7. Print the name and IQ of each student. If the IQ of the student is less than 100, print `LOW IQ` instead.
+
+```sql
+
+```
+
+8. For each student print the name and their IQ category.
+
+| IQ        | Category |
+| --------- | -------- |
+| < 100     | LOW IQ   |
+| 100 - 150 | MEDIUM   |
+| > 150     | HIGH     |
+
+```sql
+
+```
+