Joins & Relationships
UNION & UNION ALL
Combining Result Sets
💡 UNION, DO, LISTS, ko, "MERGE" karta hai, EK, LIST, mein — UNION, DUPLICATES, remove, karta hai (jaise, DO, GUEST, LISTS, MERGE, karke, DUPLICATE, naam, hataana), UNION ALL, SAARE, entries, RAKHТА, hai.
UNION, DO, YA, ZYAADA, SELECT, statements, ke, results, ko, COMBINE, karta hai — HAR, SELECT, mein, SAME, number, of, columns, aur, COMPATIBLE, data, types, HONE, CHAHIYE.
UNION ALL, DUPLICATE, check, NAHI, karta, isliye, UNION, se, FASTER, hai — agar, DUPLICATES, matter, NAHI, karte, YA, PATA, hai, ki, DUPLICATES, HONGE, HI, NAHI, UNION ALL, use, karo.
SELECT name, 'customer' AS type FROM customers
UNION
SELECT name, 'vendor' AS type FROM vendors;
-- Faster, agar duplicates, matter, nahi, karte:
SELECT email FROM active_users
UNION ALL
SELECT email FROM archived_users;➕
UNION, DO, LISTS, ko, "MERGE" karta hai, EK, LIST, mein — UNION, DUPLICATES, remove, karta hai (jaise, DO, GUEST, LISTS, MERGE, karke, DUPLICATE, naam, hataana), UNION ALL, SAARE, entries, RAKHТА, hai.
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⚡ झट से Recap
- UNION = results, combine, karta, hai, duplicates, remove, karke
- UNION ALL = duplicates, keep, karta, hai — faster, hai
- Har SELECT mein, same, number, of, columns, hone, chahiye
इस page में (2 subtopics)
UNION, ke, saath, ORDER BY, sirf, FINAL, combined, result, PAR, apply, hoti, hai (LAST, SELECT, ke, BAAD, likha, jaata, hai) — HAR, individual, SELECT, ke, ANDAR, ORDER BY, use, NAHI, ki, ja, sakti.
SELECT name FROM customers
UNION
SELECT name FROM vendors
ORDER BY name;UNION, ke, result, mein, column, names, FIRST, SELECT, statement, se, LIYE, jaate, hain — BAAD, ke, SELECT, statements, ke, column, aliases, IGNORE, ho, jaate, HAIN.
Tip: Consistency, ke, liye, HAMESHA, PEHLI, SELECT, mein, hi, clear, aliases, use, karo — WOHI, final, output, mein, DIKHENGE.