variables

rakshit087 · Jul 31, 2023 · 350bc3f · 350bc3f
1 parent c4dab03
commit 350bc3f
Showing 1 changed file with 16 additions and 0 deletions.
diff --git a/mind-map-book/src/sql/14_variables.md b/mind-map-book/src/sql/14_variables.md
@@ -1 +1,17 @@
 # Variables
+
+QUERY TO FIND MEDIAN
+
+```sql
+SET @N := 0;
+SELECT COUNT(*) FROM STATION INTO @TOTAL;
+SELECT
+    ROUND(AVG(A.LAT_N), 4)
+FROM (SELECT @N := @N +1 AS ROW_ID, LAT_N FROM STATION ORDER BY LAT_N) A
+WHERE
+    CASE WHEN MOD(@TOTAL, 2) = 0 
+            THEN A.ROW_ID IN (@TOTAL/2, (@TOTAL/2+1))
+            ELSE A.ROW_ID = (@TOTAL+1)/2
+    END
+;
+```