DOC-561-SQL-Support-Changes

docs/queryworkers/sql/advanced-commands.md

@@ -0,0 +1,125 @@
+---
+sidebar_position: 10
+title: Advanced SQL Queries
+---
+
+## Case Sensitivity
+Case-sensitivity is supported for attribute names using `"<attribute name>"`.
+Case-sensitive collections names can be used as well.
+
+Example:
+
+```sql
+SELECT "CaseSens" FROM case_sens;
+```
+
+## Join Support
+Macrometa SQL has full support for `left outer join`.
+
+Example:
+
+```sql
+SELECT category.name, avg(film.length)
+FROM film
+LEFT OUTER JOIN film_category ON (film.film_id= film_category.film_id)
+LEFT OUTER JOIN category ON (film_category.category_id = category.category_id)
+GROUP BY category.name
+ORDER BY avg(film.length) DESC
+```
+
+## WHERE and EXISTS operators
+`WHERE...EXISTS` operators also supported. It has two variants:
+- `WHERE EXISTS`
+- `WHERE NOT EXISTS`
+Both variants can be used to check subquery result.
+
+Example:
+
+```sql
+SELECT inventory.inventory_id
+FROM inventory JOIN store ON (inventory.store_id = store.store_id)
+JOIN film ON (inventory.film_id = film.film_id)
+JOIN rental ON (inventory.inventory_id = rental.inventory_id)
+WHERE film.title = 'Academy Dinosaur'
+AND store.store_id = 1
+AND NOT EXISTS (
+SELECT *
+FROM rental
+WHERE rental.inventory_id = inventory.inventory_id
+AND rental.return_date IS NULL)
+```
+
+## HAVING clause
+`HAVING` clause is supported.
+
+Example:
+
+```sql
+SELECT inventory.inventory_id
+FROM inventory JOIN store ON (inventory.store_id = store.store_id)
+JOIN film ON (inventory.film_id = film.film_id)
+JOIN rental ON (inventory.inventory_id = rental.inventory_id)
+WHERE film.title = 'Academy Dinosaur'
+AND store.store_id = 1
+AND NOT EXISTS (
+SELECT *
+FROM rental
+WHERE rental.inventory_id = inventory.inventory_id
+AND rental.return_date IS NULL)
+```
+
+:::note
+Users can't use  `HAVING` clause with subqueries.
+:::
+
+## SQL Functions
+Macrometa SQL supports following functions:
+- STDDEV
+- STDDEV_POP
+- STDDEV_SAMP
+- VAR_POP
+- VAR_SAMP
+- MEDIAN
+- PERCENTILE
+- PERCENTILE_CONT
+
+:::note
+Users can use mathematical functions such as degrees and logarithm with arbitrary base.
+:::
+
+Examples:
+
+```sql
+SELECT fl.title, FLOOR(fl.length/2.34) fl, fl.length/2.34 nfl, fl.length
+FROM film AS fl;
+```
+
+```sql
+SELECT fl.title, FLOOR(fl.length/2.34) fl, ROUND(fl.length/2.34) rnd,
+fl.length/2.34 nfl, fl.length, LOG(fl.length, 2) lg2, DEGREES(pi()) pi,
+DEGREES(pi()/4) deg45
+FROM film AS fl;
+```
+
+```sql
+SELECT STDDEV(fl.length) div, VAR_POP(fl.length) var
+FROM film AS fl;
+```
+
+:::note
+Percentile function is no **aggregation function**. We can't use it in groupings in the similar manner `STDDEV` and `VAR_POP`.
+:::
+
+Example on how to use percentile function:
+
+```sql
+select PERCENTILE((select fl.length from film as fl), 0.5) med;
+```
+
+Absolute value operator is supported.
+
+Example:
+
+```sql
+SELECT @ -123.45;
+```