Add subquery TCL tests

testing/subquery.test

@@ -446,4 +446,196 @@ do_execsql_test_on_specific_db {:memory:} subquery-cte-available-in-arbitrary-de
             from cte join cte3
         ) join cte2
     );
-} {112}
+} {112}
+
+# WHERE CLAUSE SUBQUERIES
+
+# EXISTS/NOT EXISTS
+
+do_execsql_test_on_specific_db {:memory:} subquery-exists-basic {
+    create table test(a);
+    insert into test values (1);
+    select * from test where exists (select 0);
+    select * from test where not exists (select 0 where false);
+} {1
+1}
+
+# Trivial example: get all users if there are any products
+do_execsql_test_on_specific_db {:memory:} subquery-exists-uncorrelated {
+    create table products(id, name, price);
+    create table users(id, name);
+    insert into products values (1, 'hat', 50), (2, 'cap', 75), (3, 'shirt', 100);
+    insert into users values (1, 'Alice'), (2, 'Bob'), (3, 'Charlie');
+
+    select * from users where exists (select 1 from products);
+} {1|Alice
+2|Bob
+3|Charlie}
+
+# Get all products when there are no users
+do_execsql_test_on_specific_db {:memory:} subquery-not-exists-uncorrelated {
+    create table products(id, name, price);
+    create table users(id, name);
+    insert into products values (1, 'hat', 50), (2, 'cap', 75);
+
+    select * from products where not exists (select 1 from users);
+} {1|hat|50
+2|cap|75}
+
+# Get products that have a matching category
+do_execsql_test_on_specific_db {:memory:} subquery-exists-correlated {
+    create table products(id, name, category_id);
+    create table categories(id, name);
+    insert into products values (1, 'hat', 10), (2, 'cap', 20), (3, 'shirt', 10);
+    insert into categories values (10, 'Clothing'), (30, 'Electronics');
+
+    select * from products p where exists (
+        select * from categories c where c.id = p.category_id
+    );
+} {1|hat|10
+3|shirt|10}
+
+# Get users who have no orders
+do_execsql_test_on_specific_db {:memory:} subquery-not-exists-correlated {
+    create table users(id, name, age);
+    create table orders(id, user_id, amount);
+    insert into users values (1, 'Alice', 25), (2, 'Bob', 30), (3, 'Charlie', 35);
+    insert into orders values (1, 1, 100), (2, 3, 200);
+
+    select * from users u where not exists (
+        select * from orders o where o.user_id = u.id
+    );
+} {2|Bob|30}
+
+# Get products that belong to the 'Clothing' category
+do_execsql_test_on_specific_db {:memory:} subquery-exists-with-conditions {
+    create table categories(id, name);
+    create table products(id, name, price, category_id);
+    insert into categories values (1, 'Clothing'), (2, 'Electronics');
+    insert into products values (1, 'hat', 50, 1), (2, 'cap', 25, 1), (3, 'macbook', 75, 2);
+
+    select * from products p where exists (
+        select * from categories c 
+        where c.id = p.category_id and c.name = 'Clothing'
+    );
+} {1|hat|50|1
+2|cap|25|1}
+
+# Get users who have products with high-rated reviews
+do_execsql_test_on_specific_db {:memory:} subquery-nested-exists {
+    create table users(id, name);
+    create table products(id, name, user_id);
+    create table reviews(id, product_id, rating);
+    insert into users values (1, 'Alice'), (2, 'Bob');
+    insert into products values (1, 'hat', 1), (2, 'cap', 2);
+    insert into reviews values (1, 1, 5);
+
+    select * from users u where exists (
+        select * from products p where p.user_id = u.id and exists (
+            select 1 from reviews r where r.product_id = p.id and r.rating >= 4
+        )
+    );
+} {1|Alice}
+
+# Get products that have tags (none exist, so empty result)
+do_execsql_test_on_specific_db {:memory:} subquery-exists-empty-result {
+    create table products(id, name);
+    create table tags(product_id, tag);
+    insert into products values (1, 'hat'), (2, 'cap');
+
+    select * from products p where exists (
+        select * from tags t where t.product_id = p.id
+    );
+} {}
+
+# Get users whose emails are not in the blocked list
+do_execsql_test_on_specific_db {:memory:} subquery-not-exists-all-match {
+    create table users(id, email);
+    create table blocked_emails(email);
+    insert into users values (1, 'alice@test.com'), (2, 'bob@test.com');
+    insert into blocked_emails values ('spam@test.com');
+
+    select * from users u where not exists (
+        select * from blocked_emails b where b.email = u.email
+    );
+} {1|alice@test.com
+2|bob@test.com}
+
+# SCALAR SUBQUERIES
+
+# Get products with price higher than average price
+do_execsql_test_on_specific_db {:memory:} subquery-scalar-comparison {
+    create table products(id, name, price);
+    insert into products values (1, 'hat', 50), (2, 'cap', 25), (3, 'jacket', 75);
+
+    select * from products where price >= (
+        select avg(price) from products
+    );
+} {1|hat|50
+3|jacket|75}
+
+# Get users with the highest score
+do_execsql_test_on_specific_db {:memory:} subquery-scalar-max {
+    create table users(id, name, score);
+    insert into users values (1, 'Alice', 85), (2, 'Bob', 92), (3, 'Charlie', 92);
+
+    select * from users where score = (
+        select max(score) from users
+    );
+} {2|Bob|92
+3|Charlie|92}
+
+# (x,y) IN SUBQUERIES
+
+# Get products from specific categories using IN
+do_execsql_test_on_specific_db {:memory:} subquery-in-single-column {
+    create table products(id, name, category_id);
+    create table categories(id, name);
+    insert into categories values (1, 'Clothing'), (2, 'Electronics'), (3, 'Books');
+    insert into products values (1, 'hat', 1), (2, 'laptop', 2), (3, 'novel', 3), (4, 'cap', 1);
+
+    select * from products where category_id in (
+        select id from categories where name in ('Clothing', 'Electronics')
+    );
+} {1|hat|1
+2|laptop|2
+4|cap|1}
+
+# Get products NOT in discontinued categories
+do_execsql_test_on_specific_db {:memory:} subquery-not-in-single-column {
+    create table products(id, name, category_id);
+    create table discontinued_categories(category_id);
+    insert into products values (1, 'hat', 1), (2, 'laptop', 2), (3, 'book', 3);
+    insert into discontinued_categories values (2);
+
+    select * from products where category_id not in (
+        select category_id from discontinued_categories
+    );
+} {1|hat|1
+3|book|3}
+
+# Get order items matching specific product-quantity combinations
+do_execsql_test_on_specific_db {:memory:} subquery-in-multiple-columns {
+    create table order_items(order_id, product_id, quantity);
+    create table special_offers(product_id, min_quantity);
+    insert into order_items values (1, 10, 5), (2, 20, 3), (3, 10, 2), (4, 30, 1);
+    insert into special_offers values (10, 5), (20, 3);
+
+    select * from order_items where (product_id, quantity) in (
+        select product_id, min_quantity from special_offers
+    );
+} {1|10|5
+2|20|3}
+
+# Get users whose (name, age) combination is not in the restricted list
+do_execsql_test_on_specific_db {:memory:} subquery-not-in-multiple-columns {
+    create table users(id, name, age);
+    create table restricted_profiles(name, age);
+    insert into users values (1, 'Alice', 25), (2, 'Bob', 30), (3, 'Charlie', 25);
+    insert into restricted_profiles values ('Bob', 30);
+
+    select * from users where (name, age) not in (
+        select name, age from restricted_profiles
+    );
+} {1|Alice|25
+3|Charlie|25}