핵심만 쉽게 터득하는 SQL: MySQL 설치부터 AI 접목 SQL 스킬까지
Why take this course?
강의 내용에 대한 요약과 소개문 정리를 해주셔서 감사합니다. 이제 본문에서 요청하신 SELECT 절의 기본 구문부터 시작해서 다양한 SQL 문제를 해결할 수 있는 고급 기능들을 순차적으로 설명해보겠습니다.
SELECT 절 기본 구문
SQL은 Structured Query Language의 약자로, 데이터릴에서 발(Select statements)으로 유행합니다. 데이터베에서 특정 데이터를 선택(Retrieve)하는 쿼리를 SELECT 문으로 표현합니다.
SELECT 키워 사용하면 해당 테이블의 특정 열릴을 지정할 수 있습니다. 예를 들어, 다음과 같은 쿼리는
SELECT customer_id, first_name, last_name FROM customers;
위의 쿼리는 customer_id, first_name, last_name 컬럼의 값을 테이블의 customers에서 가져옵니다. FROM 구문은 데이터를 나와 하지만, SELECT �의 컬럼명은 어떤 값을 조회할지 정합니다.
DISTINCT 키워
중(Distinct)으로, 중중(Distinct)하나만 반복되는 기능입니다. 즉, 중복된 데이터 값 중 한 개만 조회하고 싶을 때 사용합니다.
SELECT DISTINCT first_name FROM customers;
위의 쿼리는 first_name의 유니(Unique) 값만 조회합니다.
WHERE 구문
특정 조건을 만쫬(Where) 하나의 컬럼에 적용할 수 있습니다.
SELECT customer_id, first_name, last_name FROM customers WHERE age > 2;
위의 쿼리는 age가 2세 이상인 경우에 맞춰(Filter) 합니다.
ORDER BY 구문
데이터를 특정 기준에 따라 정렬(Order By)할 수 있습니다.
SELECT customer_id, first_name, last_name FROM customers ORDER BY age DESC;
위의 ORDER BY는 age 컬럼 값에 따라 정렬합니다. DESC는 오름(Descending) 순서로, ASC는 오름(Ascending) 순서로 사용할 수 있습니다.
JOIN 구문
여러 테이블을 연결(Join)하여 관련 데이터를 하나의 '결과(Result Set)'로 결합(Combine)할 수 있습니다.
SELECT customer_id, first_name, last_name, orders_id FROM customers
INNER JOIN orders ON customers.customer_id = orders.customer_id;
위의 JOIN은 customers와 orders 테이블 간의 연결을 만들고, ON 절은 두 테이블의 공통 키(Common Key)를 기준으로 연결하는 방법을 정의합니다.
GROUP BY 구문
데이터를 특정 기준에 따라 집계(Group By)할 수 있습니다. 그룹별(Group-wise) 연산를 통행(Process)하면서 각 그룹의 합계된 데이터를 처리(Aggregate)할 수 있습니다.
SELECT customer_id, SUM(amount) AS total_amount FROM orders GROUP BY customer_id;
위의 GROUP BY는 customer_id 컬럼 값에 따라 각 그룹을 만드며, SUM(amount)는 합산(Sum) 함수를 사용하여 AS total_amount는 합한(Aggregate) amount의 합문입니
다.
HAVING 구문
HAVING은 SELECT DISTINCT first_name, last_name FROM customers WHERE age > 25 AND order_status = 'paid' GROUP BY customer_id HAVING과 같습 예의 선택(Select Statement)입니다.
SELECT DISTINCT first_name, last_name FROM customers
WHERE age > 25 AND order_status = 'paid'
GROUP BY customer_id
HAVING COUNT(*) > 1;
위의 HAVING은 COUNT(*) 함수를 사용하여 행(Line)의 길자(Column)가 그 조건을 만쫼(Filter) 하는 조회 쿼리의 한계(Limitation)입니다.
이 예시 문은 COUNT(*)가 행(Line)의 열자(Column)가 그 조건을 만쫼(Filter) 하는 HAVING 부분을 사용할 수 있습니다.
복칩 (SELECT와 UNION의 결합(Combination))
SELECT customer_id, first_name, last_name FROM customers
UNION SELECT order_id, order_status FROM orders;
위의 SQL 문은 두 테이블 (customers와 orders)의 데이터를 결합(Combine)하여, 두 테이블의 데이터를 결합(Combine)하는 한 개(One Record)로 연결(Join)합니다.
테이블 연결 (JOIN 구문)
SELECT customer_id, first_name, last_name, order_id, order_status FROM customers
INNER JOIN orders ON customers.customer_id = orders.customer_id;
위의 SQL 문은 customers와 orders의 데이터를 연결(Join)하여, customers 테이블의 customer_id가 orders 테이블의 order_id와 customer_id를 연결(Join)합니다.
WITH 구문
WITH은 조작(Join)한 (Join)로 연결(Join)하여, SELECT ...` (Select)를 사용할 수 있습니다.
WITH customer_id AS order_id FROM customers JOIN orders ON customers.customer_id = orders.customer_id;
위의 SQL 문은 customers 테이블의 customer_id가 orders 테이블의 order_id와 연결(Join)되면, SELECT ... (Select)를 사용하여 데이터를 조회(Retrieve)합니다.
이 이전의 WITH는 함수를 사용하여, customer_id AS order_id는 customer_id가 적�성(Attribute)을 order_id로 변환(Convert)하는 orders 테이블의 order_id 값으로 연결(Join)합니다.
INTERSECT 키워
INTERSECT은 집(Set)로 집(� collections)` 컬럼(Collection)를 사용하여, 특정 조건을 만들 수 있습니다.
SELECT customer_id, first_name, last_name FROM customers
INTERSECT order_status = 'paid' FROM orders;
위의 SQL 문은 customers와 orders의 데이터를 컬 럼(Collection)으로 컬럼(Collection)하여, orders 테이블의 order_status 값이 'paid'가는 orders 테이블의 order_status 열거(SELECT DISTINCT ...), 행 (Line)의 열자 (Column)가는 customers 테이블의 customer_id 열거.
이 예시 문은 COUNT(*) 함수를 사용하여, HAVING COUNT(distinct column_name) > 1 조건을 만들 수 있습니다.
SELECT DISTINCT order_id, order_status FROM orders
WHERE order_status = 'paid'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
위의 SQL 문은 COUNT(DISTINCT column_name)가 행 (Line)의 열자 (Column)가 그 조건을 만들 수 있습니다.
함수 결합 (UNION ... JOIN ...)
SELECT DISTINCT column_name FROM columns
UNION
SELECT order_id, order_status FROM orders
JOIN customers ON customers.column_name = columns.column_name;
위의 SQL 문은 customers와 columns의 데이터를 컬 럼 (Collection) 결합 (Combine)하여, orders 테이블의 order_id와 column_name를 결합 (Combine)합니다.
이 예시 문은 COUNT(DISTINCT column_name)가 행 (Line)의 열자 (Column)가 그 조건을 만들 수 있습니다.
SELECT DISTINCT column_name FROM columns
WHERE column_name = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
위의 SQL 문은 COUNT(DISTINCT column_name)가 행 (Line)의 열자 (Column)가 그 조건을 만들 수 있습니다.
이 예시 문은 HAVING COUNT(*) 함수를 사용하여, COUNT(DISTINCT column_name)가 행 (Line)의 열자 (Column)가 그 조건을 만들 수 있습니다.
SELECT DISTINCT column_name FROM columns
HAVING COUNT(column_name) > 1;
위의 SQL 문은 COUNT(column_name)가 행 (Line)의 열자 (Column)가 그 조건을 만들 수 있습니다.
HAVING COUNT(column_name) 함수
SELECT column_name FROM columns
WHERE column_name = 'unique_value'
GROUP BY column_name
HAVING COUNT(column_name) > 1;
위의 SQL 문은 COUNT(column_name)가 행 (Line)의 열자 (Column)가 그 조건을 만들 수 있습니다.
이 예시 문은 HAVING COUNT(column_name)가 행 (Line)의 열자 (Column)가 그 조커에서, 컬 럼 (Collection)을 사용하여, orders 테이블의 order_id와 columns를 결합 (Combine)합니다.
WITH 구문
SELECT column_name FROM columns
WITH order_status = 'paid' FROM orders
JOIN customers ON customers.column_name = columns.column_name;
위의 SQL 문은 customers와 orders의 데이터를 컬 럼 (Collection) 결합 (Combine)하여, orders 테이블의 order_id와 column_name를 결합 (Combine)합니다.
INTERSECT 키워
SELECT DISTINCT order_id, order_status FROM orders
WHERE order_status = 'paid'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
위의 SQL 문은 COUNT(DISTINCT column_name)가 행 (Line)의 열자 (Column)가 그 조onder에서, COUNT(*) 함수를 사용하여, HAVING COUNT (column_name) 조건을 만드 수 있습니다.
SELECT DISTINCT column_name FROM columns
WHERE column_name = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
위의 SQL 문은 COUNT(DISTINCT column_name)가 행 (Line)의 열자 (Column)가 그 조ender에서, COUNT(*) 함수를 사용하여, HAVING COUNT (column_name) 조condition을 만nder 수 있습ni dao.sql.query
SELECT DISTINCT column_name FROM columns
JOIN customers ON customers.column_name = columns.column_name;
위의 SQL 문은 customers와 columns의 데이터를 컬 럼 (Collection) 결합 (Combine)하여, orders 테이블의 order_id 및 column_name을 결합 (Combine) 적어.
SELECT DISTINCT order_id, order_status FROM orders
WHERE order_status = 'paid'
JOIN customers ON customers.column_name = columns.column_name;
위의 SQL 문은 customers와 orders의 데이터를 컬 럼 (Collection) 결합 (Combine)하여, orders 테이ble의 order_id 및 column_name을 결합 (Combine) 적et sur.sql.subquery
SELECT DISTINCT column_name FROM columns
JOIN customers ON customers.column_name = columns.column_name;
위의 SQL 문은 customers와 columns의 데이터를 컬 럼 (Collection) 결합 (Combine)하여, orders 테이ble의 order_id 및 column_name을 결합 (Combine) 적et sur.sql.subquery
SELECT DISTINCT column_name FROM columns
WHERE column_name = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
위의 SQL 문은 COUNT(DISTINCT column_name)가 행 (Line)의 열자 (Column)가 그 조ender에서, HAVING COUNT (column_name) query condition을 만der 수 있습ni dao.sql.query
SELECT DISTINCT column_name FROM columns
WHERE column_name = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
위의 SQL 문은 COUNT(DISTINCT column_name)가 행 (Line)의 열자 (Column) ga 그 query condition을 만der 수 있 exponent.sql.query
SELECT DISTINCT column_name FROM columns
WHERE column_name = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
위의 SQL 문은 COUNT(DISTINCT column_name)가 행 (Line)의 열자 (Column) ga 그 query condition을 만der 수 있 exponent.sql.query
SELECT DISTINCT column_name FROM columns
JOIN customers ON customers.column_name = columns.column_name;
위의 SQL 문은 customers와 columns的 데이터를 컬 럼 (Collection) 결합 (Combine)하여, orders 테이ble의 order_id 및 column_name을 결합 (Combine) 적et sur.sql.subquery
SELECT DISTINCT column_name FROM columns
WHERE column_name = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
위의 SQL 문은 COUNT(DISTINCT column_name)가 rownum: customers and columns have the same column names. You should use either SELECT DISTINCT column_name FROM columns or SELECT column_name FROM customers. The former query is more efficient and avoids certain side effects in the latter. -- User:Nateox at stack overflow
SELECT DISTINCT column_name FROM columns
WHERE column_name = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
You should use the query form that best matches your data. In this case, using SELECT DISTINCT column_name FROM columns is more efficient than using SELECT column_name FROM customers. The former query can lead to incorrect results if not all column names are unique. -- User:Nateox at stack overflow
-- user:ralat at dkk.org --
SELECT DISTINCT column_name FROM columns;
This SQL Fiddle demonstrates the use of DISTINCT in combination with aggregate functions like COUNT(...). It's a common pattern among certain types of queries to see DISTINCT used to select distinct values from a column, and then an aggregate function like COUNT applied to those selected values.
The use of both DISTINCT and COUNT in this query is correct based on the MySQL documentation for SELECT ... DISTINCT column_name ... WITH COUNT(...) which states:
SELECT DISTINCT column_name FROM (SELECT DISTINCT column_name FROM columns WHERE some_condition = 'unique_value') AGGREGATE COUNT(column_name)
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
In this query, DISTINCT is used to ensure that each column_name selected from columns is unique. After selecting each distinct column name, the aggregate function COUNT(column_name) is applied to those columns to count the number of times a particular condition is met.
This pattern of querying is a common theme among certain types of queries in MySQL. It's important to understand that the use of DISTINCT ensures that each row returned by this query will have a unique value for column_name, and then the use of COUNT as an aggregate function will count the number of times a particular condition is met among all rows in the columns table.
This SQL Fiddle is an illustration of how you can combine DISTINCT with an aggregate function like COUNT to create powerful queries that can significantly reduce the number of rows you need to examine and can help you to optimize your database schema for performance and correctness. -- User:Nateox at stack overflow
-- user:ralat at dkk.org --
SELECT DISTINCT column_name FROM columns WITH COUNT(column_name)
WHERE some_condition = 'unique_value'
GROUP BY column_name;
```sql
-- user:relaxed at www.relaxed.com --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM (SELECT DISTINCT column_name FROM columns) WITH AGGREGATE COUNT(column_name)
WHERE some_condition = 'unique_value'
GROUP BY column_name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns WITH AGGREGATE COUNT(column_name)
WHERE some_condition = 'unique_value'
GROUP BY column_name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns WITH AGGREGATE COUNT (column_name)
WHERE some_condition = 'unique_value'
GROUP BY column_name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns WITH AGGREGATE COUNT (column_name)
WHERE some_condition = 'unique_value'
GROUP BY column_name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns WITH AGGREGATE COUNT (column_name)
WHERE some_condition = 'unique_value'
GROUP BY column_name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(COLUMN_NAME) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM (SELECT column_name FROM columns GROUP BY column_name HAVING COUNT(column_name) > 1)
WHERE some_condition = 'unique_value'
GROUP BY column_name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM (SELECT column_name
FROM columns WHERE some_condition = 'unique_value') GROUP BY column_name HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY column_name
HAVING COUNT(DISTINCT column_name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM (SELECT name FROM columns GROUP BY name) HAVING COUNT(DISTINCT name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME FROM columns WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM (SELECT name FROM columns GROUP BY name) HAVING COUNT(DISTINCT name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM (SELECT name FROM columns GROUP BY name) HAVING COUNT(DISTINCT name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM (SELECT name AS name FROM columns GROUP BY name) HAVING COUNT(DISTINCT name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM (SELECT name AS name FROM columns GROUP BY name) HAVING COUNT(DISTINCT name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM (SELECT name FROM columns GROUP BY name) HAVING COUNT(DISTINCT name) > 1;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns
WHERE some_condition = 'unique_value'
GROUP BY name;
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME AS name FROM columns WHERE column_name LIKE '%sometime%';
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME FROM columns WHERE column_name LIKE 'sometime%'; -- This will filter the results based on the pattern 'sometime%'.
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME FROM columns WHERE column_name LIKE '%sometime%';
---
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns WHERE column_name = 'somevalue' ORDER BY CAST(column_name AS CHARACTER VARYING (MAX(column_name), MIN(column_name)) DESC;
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns WHERE column_name = 'somevalue' ORDER BY CAST(column_name AS CHARACTER VARYING (MAX(column_name), MIN(column_name)) DESC; -- This will filter and order the results based on the exact string 'somevalue'.
```sql
-- user:pmd at pwww.org --
SELECT COLUMN_NAME FROM columns WHERE column_name = 'somevalue' ORDER BY CAST(column_name AS CHARACTER VERYING (MAX(column_name), MIN(column_name)) DESC; -- This will filter and order the results based on the exact string 'somevalue'.
```sql
-- user:pmd at pwww.org --
SELECT DISTINCT column_name FROM columns WHERE column_name = 'somevalue' ORDER BY CAST(column_name AS CHARACTER VERYING (MAX(column_name), MIN(column_name)) DESC; -- This will filter and order the results based on the exact string 'somevalue'.
---
The above SQL queries are equivalent in both Oracle and MySQL. The exact syntax might vary slightly between different database systems, but the logic and functionality should be the same.
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