diff --git a/SQL/Advanced Select/1-the-pads.sql b/SQL/Advanced Select/1-the-pads.sql
new file mode 100644
index 0000000..b62d770
--- /dev/null
+++ b/SQL/Advanced Select/1-the-pads.sql	
@@ -0,0 +1,2 @@
+select concat(Name, '(', SUBSTRING(Occupation, 1, 1), ')') from OCCUPATIONS order by Name;
+select concat('There are total ', count(*), ' ', lower(Occupation), 's.') from OCCUPATIONS group by Occupation order by count(*) ASC, Occupation ASC;
diff --git a/SQL/Advanced Select/2-occupations.sql b/SQL/Advanced Select/2-occupations.sql
new file mode 100644
index 0000000..7e328ea
--- /dev/null
+++ b/SQL/Advanced Select/2-occupations.sql	
@@ -0,0 +1,28 @@
+# brain not work for this.
+SELECT
+  IFNULL(empId,'Totals') AS EmpId,       -- outer query labels rollup row
+  sums.2005, sums.2006, sums.2007,       -- and calculates horizontal sums
+  sums.2005 + sums.2006 + sums.2007 AS Sums
+FROM (                                   -- inner query groups by employee
+  SELECT                                 -- with an expression for each column
+    EmpID,
+    SUM(IF(Yr=2005,sales,0)) As '2005',
+    SUM(IF(Yr=2006,sales,0)) As '2006',
+    SUM(IF(Yr=2007,sales,0)) As '2007'
+  FROM Sales
+  GROUP BY EmpID WITH ROLLUP
+) AS sums;
+
+SELECT
+    pivot.Doctor, pivot.Professor,
+    pivot.Single, pivot.Actor
+FROM (
+    SELECT
+        IF(Occupation='Doctor',Name,NULL) AS 'Doctor',
+        IF(Occupation='Professor',Name,NULL) AS 'Professor',
+        IF(Occupation='Single',Name,NULL) AS 'Single',
+        IF(Occupation='Actor',Name,NULL) AS 'Actor'
+    FROM OCCUPATIONS
+    HAVING count(*) = count(Name)
+    ORDER BY Name
+) as pivot;
diff --git a/SQL/Advanced Select/3-binary-search-tree-1.sql b/SQL/Advanced Select/3-binary-search-tree-1.sql
new file mode 100644
index 0000000..3f36a6d
--- /dev/null
+++ b/SQL/Advanced Select/3-binary-search-tree-1.sql	
@@ -0,0 +1,8 @@
+SELECT N,
+CASE
+WHEN P is NULL THEN 'Root'
+WHEN N in (SELECT P FROM BST) THEN 'Inner'
+ELSE 'Leaf'
+END
+FROM BST
+ORDER by N;
diff --git a/SQL/Advanced Select/4-what-type-of-triangle.sql b/SQL/Advanced Select/4-what-type-of-triangle.sql
new file mode 100644
index 0000000..87faa92
--- /dev/null
+++ b/SQL/Advanced Select/4-what-type-of-triangle.sql	
@@ -0,0 +1,8 @@
+SELECT
+CASE
+WHEN (A + B <= C) OR (A + C <= B) OR (B + C < A) THEN 'Not A Triangle'
+WHEN (A = B) AND (A = C) THEN 'Equilateral'
+WHEN (A != B) AND (A != C) AND (B != C) THEN 'Scalene'
+ELSE 'Isosceles'
+END
+FROM TRIANGLES
diff --git a/SQL/Aggregation/1-revising-aggregations-the-count-function.sql b/SQL/Aggregation/1-revising-aggregations-the-count-function.sql
new file mode 100644
index 0000000..0bf36fc
--- /dev/null
+++ b/SQL/Aggregation/1-revising-aggregations-the-count-function.sql
@@ -0,0 +1 @@
+select count(*) from CITY WHERE POPULATION > 100000;
diff --git a/SQL/Aggregation/10-weather-observation-station-15.sql b/SQL/Aggregation/10-weather-observation-station-15.sql
new file mode 100644
index 0000000..5fb8779
--- /dev/null
+++ b/SQL/Aggregation/10-weather-observation-station-15.sql
@@ -0,0 +1 @@
+select round(LONG_W, 4) from STATION where LAT_N = (select max(LAT_N) from STATION where LAT_N < 137.2345);
diff --git a/SQL/Aggregation/11-weather-observation-station-16.sql b/SQL/Aggregation/11-weather-observation-station-16.sql
new file mode 100644
index 0000000..cf7ac0c
--- /dev/null
+++ b/SQL/Aggregation/11-weather-observation-station-16.sql
@@ -0,0 +1 @@
+select round(min(LAT_N), 4) from STATION WHERE LAT_N > 38.7780;
diff --git a/SQL/Aggregation/12-weather-observation-station-17.sql b/SQL/Aggregation/12-weather-observation-station-17.sql
new file mode 100644
index 0000000..7254c87
--- /dev/null
+++ b/SQL/Aggregation/12-weather-observation-station-17.sql
@@ -0,0 +1 @@
+select round(LONG_W, 4) from STATION WHERE LAN_T = (select min(LAT_N) from STATION WHERE LAT_N > 38.7780);
diff --git a/SQL/Aggregation/13-weather-observation-station-18.sql b/SQL/Aggregation/13-weather-observation-station-18.sql
new file mode 100644
index 0000000..225af16
--- /dev/null
+++ b/SQL/Aggregation/13-weather-observation-station-18.sql
@@ -0,0 +1 @@
+select round(ABS(MIN(LAT_N) - MIN(LONG_W)) + ABS(MAX(LAT_N) - MAX(LONG_W)), 4) from STATION;
diff --git a/SQL/Aggregation/14-weather-observation-station-19.sql b/SQL/Aggregation/14-weather-observation-station-19.sql
new file mode 100644
index 0000000..ba3e8f2
--- /dev/null
+++ b/SQL/Aggregation/14-weather-observation-station-19.sql
@@ -0,0 +1 @@
+select round(SQRT(POW(MIN(LAT_N) - MIN(LONG_W), 2) + POW(MAX(LAT_N) - MAX(LONG_W), 2)), 4) from STATION;
diff --git a/SQL/Aggregation/15-weather-observation-station-20.sql b/SQL/Aggregation/15-weather-observation-station-20.sql
new file mode 100644
index 0000000..0694ba4
--- /dev/null
+++ b/SQL/Aggregation/15-weather-observation-station-20.sql
@@ -0,0 +1,6 @@
+SELECT ROUND(x.LAT_N,4) from
+STATION x, STATION y
+GROUP BY x.LAT_N
+HAVING SUM(SIGN(1-SIGN(y.LAT_N-x.LAT_N)))/COUNT(*) > .5 LIMIT 1
+
+# sql over. i can't solve them.
diff --git a/SQL/Aggregation/2-revising-aggregations-sum.sql b/SQL/Aggregation/2-revising-aggregations-sum.sql
new file mode 100644
index 0000000..dc12cab
--- /dev/null
+++ b/SQL/Aggregation/2-revising-aggregations-sum.sql
@@ -0,0 +1 @@
+select sum(POPULATION) from CITY WHERE DISTRICT = 'California';
diff --git a/SQL/Aggregation/3-revising-aggregations-the-average-function.sql b/SQL/Aggregation/3-revising-aggregations-the-average-function.sql
new file mode 100644
index 0000000..83cca6b
--- /dev/null
+++ b/SQL/Aggregation/3-revising-aggregations-the-average-function.sql
@@ -0,0 +1 @@
+select avg(POPULATION) from CITY WHERE DISTRICT = 'California';
diff --git a/SQL/Aggregation/4-average-population.sql b/SQL/Aggregation/4-average-population.sql
new file mode 100644
index 0000000..ba04642
--- /dev/null
+++ b/SQL/Aggregation/4-average-population.sql
@@ -0,0 +1 @@
+select FLOOR(avg(POPULATION)) from CITY;
diff --git a/SQL/Aggregation/5-japan-population.sql b/SQL/Aggregation/5-japan-population.sql
new file mode 100644
index 0000000..2c7d0dd
--- /dev/null
+++ b/SQL/Aggregation/5-japan-population.sql
@@ -0,0 +1 @@
+SELECT SUM(POPULATION) FROM CITY WHERE COUNTRYCODE = 'JPN';
diff --git a/SQL/Aggregation/6-population-density-difference.sql b/SQL/Aggregation/6-population-density-difference.sql
new file mode 100644
index 0000000..8769fab
--- /dev/null
+++ b/SQL/Aggregation/6-population-density-difference.sql
@@ -0,0 +1 @@
+SELECT max(POPULATION) - min(POPULATION) FROM CITY;
diff --git a/SQL/Aggregation/7-weather-observation-station-2.sql b/SQL/Aggregation/7-weather-observation-station-2.sql
new file mode 100644
index 0000000..a36e48e
--- /dev/null
+++ b/SQL/Aggregation/7-weather-observation-station-2.sql
@@ -0,0 +1 @@
+select concat(ROUND(sum(LAT_N),2), ' ', ROUND(sum(LONG_W),2)) from STATION;
diff --git a/SQL/Aggregation/8-weather-observation-station-13.sql b/SQL/Aggregation/8-weather-observation-station-13.sql
new file mode 100644
index 0000000..dd2db1f
--- /dev/null
+++ b/SQL/Aggregation/8-weather-observation-station-13.sql
@@ -0,0 +1 @@
+select truncate(sum(LAT_N), 4) from STATION where LAT_N < 137.2345 AND LAT_N > 38.7880;
diff --git a/SQL/Aggregation/9-weather-observation-station-14.sql b/SQL/Aggregation/9-weather-observation-station-14.sql
new file mode 100644
index 0000000..70a1074
--- /dev/null
+++ b/SQL/Aggregation/9-weather-observation-station-14.sql
@@ -0,0 +1 @@
+select truncate(max(LAT_N), 4) from STATION where LAT_N < 137.2345;
diff --git a/SQL/Basic Select/1-revising-the-select-query.sql b/SQL/Basic Select/1-revising-the-select-query.sql
new file mode 100644
index 0000000..f5e1d2e
--- /dev/null
+++ b/SQL/Basic Select/1-revising-the-select-query.sql	
@@ -0,0 +1 @@
+select * from CITY where POPULATION > 100000 and COUNTRYCODE = 'USA';
diff --git a/SQL/Basic Select/10-weather-observation-station-5.sql b/SQL/Basic Select/10-weather-observation-station-5.sql
new file mode 100644
index 0000000..1823825
--- /dev/null
+++ b/SQL/Basic Select/10-weather-observation-station-5.sql	
@@ -0,0 +1,2 @@
+select city, length(city) from station order by length(city) limit 1;
+select city, length(city) from station order by length(city) desc limit 1;
diff --git a/SQL/Basic Select/11-weather-observation-station-6.sql b/SQL/Basic Select/11-weather-observation-station-6.sql
new file mode 100644
index 0000000..84b4fa8
--- /dev/null
+++ b/SQL/Basic Select/11-weather-observation-station-6.sql	
@@ -0,0 +1 @@
+select DISTINCT CITY from STATION WHERE (CITY LIKE 'A%' OR CITY LIKE 'E%' OR CITY LIKE 'I%' OR CITY LIKE 'O%' OR CITY LIKE 'U%');
diff --git a/SQL/Basic Select/12-weather-observation-station-7.sql b/SQL/Basic Select/12-weather-observation-station-7.sql
new file mode 100644
index 0000000..08fb750
--- /dev/null
+++ b/SQL/Basic Select/12-weather-observation-station-7.sql	
@@ -0,0 +1 @@
+select DISTINCT CITY from STATION WHERE (CITY LIKE '%A' OR CITY LIKE '%E' OR CITY LIKE '%I' OR CITY LIKE '%O' OR CITY LIKE '%U');
diff --git a/SQL/Basic Select/13-weather-observation-station-8.sql b/SQL/Basic Select/13-weather-observation-station-8.sql
new file mode 100644
index 0000000..269e7c7
--- /dev/null
+++ b/SQL/Basic Select/13-weather-observation-station-8.sql	
@@ -0,0 +1,2 @@
+# sql serve
+select DISTINCT CITY from STATION WHERE CITY LIKE '[AEIOU]%[AEIOU]';
diff --git a/SQL/Basic Select/14-weather-observation-station-9.sql b/SQL/Basic Select/14-weather-observation-station-9.sql
new file mode 100644
index 0000000..db39d19
--- /dev/null
+++ b/SQL/Basic Select/14-weather-observation-station-9.sql	
@@ -0,0 +1,3 @@
+# sql serve
+select DISTINCT CITY from STATION WHERE CITY RLIKE '[^AEIOUaeiou]%';
+select DISTINCT CITY from STATION WHERE CITY LIKE '[^AEIOU]%';
diff --git a/SQL/Basic Select/15-weather-observation-station-10.sql b/SQL/Basic Select/15-weather-observation-station-10.sql
new file mode 100644
index 0000000..640053c
--- /dev/null
+++ b/SQL/Basic Select/15-weather-observation-station-10.sql	
@@ -0,0 +1 @@
+select DISTINCT CITY from STATION WHERE CITY LIKE '%[^AEIOU]';
diff --git a/SQL/Basic Select/16-weather-observation-station-11.sql b/SQL/Basic Select/16-weather-observation-station-11.sql
new file mode 100644
index 0000000..b6f5bd8
--- /dev/null
+++ b/SQL/Basic Select/16-weather-observation-station-11.sql	
@@ -0,0 +1 @@
+select DISTINCT CITY from STATION WHERE CITY LIKE '[^AEIOU]%' OR CITY LIKE '%[^AEIOU]';
diff --git a/SQL/Basic Select/17-weather-observation-station-12.sql b/SQL/Basic Select/17-weather-observation-station-12.sql
new file mode 100644
index 0000000..74155ba
--- /dev/null
+++ b/SQL/Basic Select/17-weather-observation-station-12.sql	
@@ -0,0 +1 @@
+select DISTINCT CITY from STATION WHERE CITY LIKE '[^AEIOU]%[^AEIOU]';
diff --git a/SQL/Basic Select/18-more-than-75-marks.sql b/SQL/Basic Select/18-more-than-75-marks.sql
new file mode 100644
index 0000000..9cddd8d
--- /dev/null
+++ b/SQL/Basic Select/18-more-than-75-marks.sql	
@@ -0,0 +1 @@
+select Name from STUDENTS where Marks > 75 order by substr(Name, -3) ASC, ID ASC
diff --git a/SQL/Basic Select/2-revising-the-select-query-2.sql b/SQL/Basic Select/2-revising-the-select-query-2.sql
new file mode 100644
index 0000000..76b0138
--- /dev/null
+++ b/SQL/Basic Select/2-revising-the-select-query-2.sql	
@@ -0,0 +1 @@
+select NAME from CITY where POPULATION > 120000 and COUNTRYCODE = 'USA';
diff --git a/SQL/Basic Select/3-select-all-sql.sql b/SQL/Basic Select/3-select-all-sql.sql
new file mode 100644
index 0000000..cd9be6f
--- /dev/null
+++ b/SQL/Basic Select/3-select-all-sql.sql	
@@ -0,0 +1 @@
+select * from CITY;
diff --git a/SQL/Basic Select/4-select-by-id.sql b/SQL/Basic Select/4-select-by-id.sql
new file mode 100644
index 0000000..a984c33
--- /dev/null
+++ b/SQL/Basic Select/4-select-by-id.sql	
@@ -0,0 +1 @@
+select * from CITY WHERE ID = 1661;
diff --git a/SQL/Basic Select/5-japanese-cities-detail.sql b/SQL/Basic Select/5-japanese-cities-detail.sql
new file mode 100644
index 0000000..35309dc
--- /dev/null
+++ b/SQL/Basic Select/5-japanese-cities-detail.sql	
@@ -0,0 +1,2 @@
+select * from CITY WHERE COUNTRYCODE = 'JPN'
+select * from CITY WHERE COUNTRYCODE = 'JPN';
diff --git a/SQL/Basic Select/6-japanese-cities-name.sql b/SQL/Basic Select/6-japanese-cities-name.sql
new file mode 100644
index 0000000..72968fe
--- /dev/null
+++ b/SQL/Basic Select/6-japanese-cities-name.sql	
@@ -0,0 +1 @@
+select NAME from CITY where COUNTRYCODE = 'JPN';
diff --git a/SQL/Basic Select/7-weather-observation-station-1.sql b/SQL/Basic Select/7-weather-observation-station-1.sql
new file mode 100644
index 0000000..b8a04bb
--- /dev/null
+++ b/SQL/Basic Select/7-weather-observation-station-1.sql	
@@ -0,0 +1 @@
+select DISTINCT(CITY) from STATION where ID % 2 = 0 ORDER by CITY DESC;
diff --git a/SQL/Basic Select/8-weather-observation-station-3.sql b/SQL/Basic Select/8-weather-observation-station-3.sql
new file mode 100644
index 0000000..b8a04bb
--- /dev/null
+++ b/SQL/Basic Select/8-weather-observation-station-3.sql	
@@ -0,0 +1 @@
+select DISTINCT(CITY) from STATION where ID % 2 = 0 ORDER by CITY DESC;
diff --git a/SQL/Basic Select/9-weather-observation-station-4.sql b/SQL/Basic Select/9-weather-observation-station-4.sql
new file mode 100644
index 0000000..40d7366
--- /dev/null
+++ b/SQL/Basic Select/9-weather-observation-station-4.sql	
@@ -0,0 +1 @@
+select count(CITY) - count(DISTINCT(CITY)) FROM STATION;