task: #3475

Author: Ivanbyone

README.md

@@ -173,6 +173,7 @@ Useful for preparing for technical interviews and improving your SQL skills.
     - [1341. Movie Rating](./leetcode/medium/1341.%20Movie%20Rating.sql)
     - [1907. Count Salary Categories](./leetcode/medium/1907.%20Count%20Salary%20Categories.sql)
     - [1934. Confirmation Rate](./leetcode/medium/1934.%20Confirmation%20Rate.sql)
+    - [3475. DNA Pattern Recognition](./leetcode/medium/3475.%20DNA%20Pattern%20Recognition.sql)
 3. [Hard](./leetcode/hard/)
     - [185. Department Top Three Salaries](./leetcode/hard/185.%20Department%20Top%20Three%20Salaries.sql)
 

leetcode/medium/3475. DNA Pattern Recognition.sql

@@ -0,0 +1,50 @@
+/*
+Question 3475. DNA Pattern Recognition 
+Link: https://leetcode.com/problems/dna-pattern-recognition/description/?envType=problem-list-v2&envId=database
+
+Table: Samples
+
++----------------+---------+
+| Column Name    | Type    | 
++----------------+---------+
+| sample_id      | int     |
+| dna_sequence   | varchar |
+| species        | varchar |
++----------------+---------+
+sample_id is the unique key for this table.
+Each row contains a DNA sequence represented as a string of characters (A, T, G, C) and the species it was collected from.
+Biologists are studying basic patterns in DNA sequences. Write a solution to identify sample_id with the following patterns:
+
+Sequences that start with ATG (a common start codon)
+Sequences that end with either TAA, TAG, or TGA (stop codons)
+Sequences containing the motif ATAT (a simple repeated pattern)
+Sequences that have at least 3 consecutive G (like GGG or GGGG)
+Return the result table ordered by sample_id in ascending order.
+*/
+
+SELECT
+    sample_id,
+    dna_sequence,
+    species,
+    (CASE
+        WHEN LEFT(dna_sequence, 3) = 'ATG'
+            THEN 1
+        ELSE 0
+    END) AS has_start,
+    (CASE
+        WHEN RIGHT(dna_sequence, 3) IN ('TAA', 'TAG', 'TGA')
+            THEN 1
+        ELSE 0
+    END) AS has_stop,
+    (CASE
+        WHEN dna_sequence ~ 'ATAT'
+            THEN 1
+        ELSE 0
+    END) AS has_atat,
+    (CASE
+        WHEN dna_sequence ~ 'GGG'
+            THEN 1
+        ELSE 0
+    END) AS has_ggg
+FROM Samples
+ORDER BY sample_id ASC