dmitry_medvedev/homework
1
0
Fork 0
Code Issues Pull Requests 1 Actions Packages Projects Releases Wiki Activity

homework, pet project DE Dmitry_Medvedev #1

Open
dmitry_medvedev wants to merge 264 commits from md_branch into main
pull from: md_branch
merge into: dmitry_medvedev:main
Conversation 19 Commits 264 Files Changed 190
+2 -2
1 changed files with 2 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Showing only changes of commit fec0f8e103 - Show all commits
mnoskov/postgresql/9. Оптимизация/4. EXPLAIN и EXPLAIN ANALYZE/DQL_explain_analyze_practice.sql
+2 -2
View File
@@ -124,8 +124,8 @@ JOIN orders o ON u.id = o.user_id
JOIN order_items oi ON o.id = oi.order_id
JOIN products p ON oi.product_id = p.id
WHERE u.country = 'RU' AND p.category = 'Электроника';
-- Порядок чтения таблиц: order_items -> products -> orders -> users
-- Количество строк: order_items - 12, products - 3, orders - 1, users - 0
-- Порядок чтения таблиц: products -> order_items -> orders -> users
-- Количество строк: products - 3, order_items - 12, orders - 1, users - 0
-- Если у country и category будут индексы, то запрос ьудет выполняться побыстре, потому что будет Index Scan, а не Seq Scan