SQL Cheatsheet

1. Basic Commands

SELECT column1, column2 FROM table;
SELECT * FROM table;                -- Select all columns
SELECT DISTINCT column FROM table;  -- Remove duplicates

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2. Filtering (WHERE Clause)

SELECT * FROM table
WHERE column = value;

WHERE column != value
WHERE column > value
WHERE column < value
WHERE column BETWEEN value1 AND value2
WHERE column IN ('A', 'B', 'C')
WHERE column LIKE 'A%'       -- Starts with A
WHERE column LIKE '%A'       -- Ends with A
WHERE column LIKE '%A%'      -- Contains A

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3. Sorting (ORDER BY)

SELECT * FROM table
ORDER BY column ASC;

ORDER BY column DESC;

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4. Limiting Results

SELECT * FROM table LIMIT 10;

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5. Aggregations

SELECT COUNT(*) FROM table;
SELECT AVG(column) FROM table;
SELECT SUM(column) FROM table;
SELECT MIN(column), MAX(column) FROM table;

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6. Grouping (GROUP BY & HAVING)

SELECT column, COUNT(*)
FROM table
GROUP BY column;

HAVING COUNT(*) > 5;    -- Filter grouped results

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7. Joins

INNER JOIN

SELECT a.col1, b.col2
FROM tableA a
INNER JOIN tableB b
ON a.id = b.id;

LEFT JOIN

SELECT *
FROM A
LEFT JOIN B
ON A.id = B.id;

RIGHT JOIN

SELECT *
FROM A
RIGHT JOIN B
ON A.id = B.id;

FULL OUTER JOIN

SELECT *
FROM A
FULL OUTER JOIN B
ON A.id = B.id;

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8. Insert

INSERT INTO table (col1, col2)
VALUES ('value1', 'value2');

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9. Update

UPDATE table
SET column = value
WHERE condition;

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10. Delete

DELETE FROM table
WHERE condition;

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11. Create Table

CREATE TABLE table_name (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    created_at DATE
);

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12. Alter Table

ALTER TABLE table ADD column_name datatype;
ALTER TABLE table DROP COLUMN column_name;
ALTER TABLE table MODIFY column_name datatype;

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13. Subqueries

SELECT name
FROM employees
WHERE id IN (
    SELECT emp_id
    FROM salaries
    WHERE amount > 50000
);

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14. Case Statements

SELECT name,
CASE
    WHEN score >= 90 THEN 'A'
    WHEN score >= 75 THEN 'B'
    ELSE 'C'
END AS grade
FROM students;

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15. Common Functions

UPPER(column)
LOWER(column)
CONCAT(col1, col2)
NOW()
COALESCE(column, 'default') -- Replace NULL