 -- Order by
-- Group by
-- Over
-- Over (Partition by)


-- 1. Row_number
-- 2. Rank
-- 3. Dense Rank

-- 4. First_value
-- 5. Last_value
-- 6. Nth_value

-- 7. Lead
-- 8. Lag

-- 9. Cume_dist
-- 10. Ntile
-- 11. Percent_rank



CREATE TABLE employee (empid INTEGER, name TEXT NOT NULL, dept TEXT NOT NULL, age INT);

INSERT INTO employee VALUES (0001, 'Clark', 'Sales1',45);
INSERT INTO employee VALUES (0001, 'Ava', 'Acc1',44);
INSERT INTO employee VALUES (0001, 'Ava', 'HR1',2);

INSERT INTO employee VALUES (0004, 'Clark', 'Sales2',25);
INSERT INTO employee VALUES (0004, 'Dave', 'Acc2',25);
INSERT INTO employee VALUES (0004, 'Ava', 'HR2',0);

INSERT INTO employee VALUES (0005, 'Clark', 'Sales3',66);
INSERT INTO employee VALUES (0005, 'Dave', 'Acc3',3);
INSERT INTO employee VALUES (0005, 'Ava', 'HR3',3);

-- select *, sqrt(age) from employee order by empid, name;

-- DEMO OF AGGREGATING FUNCTIONS
-- SELECT MIN(name) AS a, MAX(empid) AS b, AVG(dept) AS c, COUNT(*) AS d, SUM(dept) AS e FROM employee; -- 1
-- SELECT empid, MIN(age) FROM employee;                                                                -- 2 (>> throws error because we can't combine aggregated column and non-aggregated column in select 'without over or group by')
-- SELECT empid, MIN(age) OVER() FROM employee;                                                         -- 3 (we can combine aggregated column and non-aggregated column in select 'with over()')
-- SELECT empid, MIN(age) FROM employee GROUP BY empid;                                                 -- 4 (we can combine aggregated column and non-aggregated column in select 'with group by')
-- SELECT empid, MIN(age) OVER() FROM employee GROUP BY empid;



-- DEMO OF ORDER BY
-- SELECT * FROM employee ORDER BY dept;                        -- 1 (works)
-- SELECT MIN(age) FROM employee ORDER BY dept DESC;            -- 2 (works)
-- SELECT empid, MIN(age) OVER() FROM employee ORDER BY dept;   -- 3 (works)



-- DEMO OF GROUP BY
-- SELECT * FROM employee GROUP BY empid;                               -- 1 (>> throws error because group by requires (un)grouped aggregated columns or grouped unaggregated columns in select)
-- SELECT AVG(empid) FROM employee GROUP BY empid;                      -- 2 (we can select 'aggregated' version of the same column we are grouping in group by)
-- SELECT empid FROM employee GROUP BY empid;                           -- 3 (we can select 'non-aggregated' version of the same column we are grouping in group by)

-- SELECT dept, age, MIN(age) FROM employee GROUP BY empid;             -- 4 (>> throws error because group by requires aggregated columns + grouped columns (optional) 'and nothing else' in select)
-- SELECT empid, MIN(age) FROM employee GROUP BY empid;                 -- 5 (aggregated columns + grouped columns in select work with group by)

-- SELECT empid, MIN(age) OVER() FROM employee GROUP BY empid;          -- 6 (>> throws error because over has to be used only with aggregated version of 'grouped' column)
-- SELECT empid OVER() FROM employee GROUP BY empid;                    -- 7 (>> throws error because over has to be used only with 'aggregated' version of grouped column)
-- SELECT SUM(empid) OVER() FROM employee GROUP BY empid;               -- 8 (over works with aggregated version of grouped column in group by)



-- DEMO OF PARTITION BY
-- SELECT * FROM employee PARTITION BY dept;     -- 1 (>> throws error because can't be used without over)
-- SELECT dept FROM employee PARTITION BY dept;  -- 2 (>> throws error because can't be used without over)



-- DEMO OF OVER
-- SELECT empid OVER() FROM employee;                     -- 1 (>> throws error because OVER() can't be with non agg cols)
-- SELECT empid OVER() FROM employee ORDER BY empid;      -- 2 (>> throws error because OVER() can't be with non agg cols, even with order by)
-- SELECT empid OVER() FROM employee GROUP BY empid;      -- 3 (>> throws error because OVER() can't be with non agg cols, even with group by)
-- SELECT MIN(empid) OVER() FROM employee;                -- 4 (works well because OVER() can be with agg cols)
-- SELECT MIN(empid) OVER() FROM employee GROUP BY empid; -- 4 (works well because OVER() can be with agg cols, even with group by)
-- SELECT *, MIN(age) OVER() mi, MAX(age) OVER() ma, AVG(age) OVER() av, SUM(age) OVER() su, COUNT(age) OVER() co FROM employee;



-- DEMO OF OVER(PARTITION BY)
 SELECT  empid, dept, name, age,
   MIN(age) OVER(partition by empid, name) AS mi,
   MAX(age) OVER(partition by empid) AS ma,
   AVG(age) OVER(partition by name) AS av,
   SUM(age) OVER(partition by name) AS su,
   COUNT(age) OVER(partition by name) AS co
   FROM employee
   ORDER BY empid ASC;                                                  -- 1 (works)



-- DEMO OF ROW_NUMBER, RANK, DENSE_RANK
SELECT *,
ROW_NUMBER() OVER(PARTITION BY empid ORDER BY age) as row1,
RANK() OVER(PARTITION BY empid ORDER BY age) as rank1,
DENSE_RANK() OVER(PARTITION BY empid ORDER BY age) as dense1
FROM employee ORDER BY empid;



-- DEMO OF FIRST_VALUE, LAST_VALUE, NTH_VALUE
SELECT *,
FIRST_VALUE(age) OVER win AS first1,
LAST_VALUE(age) OVER win AS last1,
NTH_VALUE(age, 2) OVER win AS nth1
FROM employee
WINDOW win AS (PARTITION BY empid ORDER BY age RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING);



-- DEMO OF LEAD, LAG
SELECT *,
LEAD(age) OVER(PARTITION BY empid ORDER BY age) as next,                 -- in nth row, display value of (n+m)th row (basically mth leading row's value) with m being given in brackets. if n-m < 0 then use def value given in brackets. if no def value given, use NULL.
LAG(age, 2, "i'm default") OVER(PARTITION BY empid ORDER BY age) as prev -- in nth row, display value of (n-m)th row (basically mth lagging row's value) with m being given in brackets. if n-m > len(table) then use def value given in brackets. if no def value given, use NULL.
FROM employee ORDER BY empid;



-- DEMO OF CUME_DIST, NTILE, PERCENT_RANK
INSERT INTO employee VALUES (0005, 'Clark', 'Sales33',67);
INSERT INTO employee VALUES (0005, 'Clark', 'Sales33',68);

SELECT *,
NTILE(2) OVER win AS ntile1,          -- binning data into # of buckets given, if uneven then upper buckets prioritised
PERCENT_RANK() OVER win AS percrank1, -- %ile rank when all data points compared among each other and sorted. 1st row 0 last row mostly 1. current row's percrank = (current row's nondense rank - 1)/(total rows - 1). how much % more/less expensive, etc.
CUME_DIST() OVER win AS cumedist1     -- distri of current sets of rows compared to entire dataset. current row's cume_dist = (current row's nondense rank's higher side value/total rows). use case = which rows constitute top 30% data points.
FROM employee
WINDOW win AS (PARTITION BY empid ORDER BY age RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING); -- 1 (works) Frame Clause



-- ALL-IN-ONE
SELECT *,
ROW_NUMBER() OVER win as row1,
RANK() OVER win as rank1,
DENSE_RANK() OVER win as dense1,
FIRST_VALUE(age) OVER win AS first1,
LAST_VALUE(age) OVER win AS last1,
NTH_VALUE(age, 2) OVER win AS nth1,
LEAD(age) OVER win as lead1,
LAG(age, 2, "i'm default") OVER win as lag1,
NTILE(2) OVER win as ntile1,
PERCENT_RANK() OVER win as percrank1,
CUME_DIST() OVER win as cume1
FROM employee
WINDOW win AS (PARTITION BY empid ORDER BY age RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING);



-- DEMO OF FRAME CLAUSE
INSERT INTO employee VALUES (0001, 'Mark', 'Sales11',71);
INSERT INTO employee VALUES (0004, 'Mark', 'Sales22',78);
DELETE FROM employee WHERE age = 68;

SELECT empid, name, dept, age,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS upuf,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS upcr,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE ROWS BETWEEN UNBOUNDED PRECEDING AND 2 FOLLOWING) AS up2f,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) AS cruf,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE ROWS BETWEEN CURRENT ROW AND CURRENT ROW) AS crcr,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE ROWS BETWEEN CURRENT ROW AND 2 FOLLOWING) AS cr2f,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE ROWS BETWEEN 2 PRECEDING AND UNBOUNDED FOLLOWING) AS 2puf,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) AS 2pcr,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING) AS 2p2f
FROM employee
ORDER BY empid ASC;

SELECT empid, name, dept, age,
       MAX(age) OVER (PARTITION BY empid RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS upuf,
       MAX(age) OVER (PARTITION BY empid RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS upcr,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE RANGE BETWEEN UNBOUNDED PRECEDING AND 50 FOLLOWING) AS up50f,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) AS cruf,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE RANGE BETWEEN CURRENT ROW AND CURRENT ROW) AS crcr,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE RANGE BETWEEN CURRENT ROW AND 50 FOLLOWING) AS cr50f,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE RANGE BETWEEN 50 PRECEDING AND UNBOUNDED FOLLOWING) AS 50puf,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE RANGE BETWEEN 50 PRECEDING AND CURRENT ROW) AS 50pcr,
       MAX(age) OVER (PARTITION BY empid ORDER BY AGE RANGE BETWEEN 50 PRECEDING AND 50 FOLLOWING) AS 50p50f
FROM employee
ORDER BY empid ASC;

created 2 years ago by Rohan Ram Vaswani

MySQL online editor

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About MySQL

MySQL is a open-source, free and very popular relational database management system which is developed, distributed and supported by Oracle corporation.

Key Features:

Open-source relational database management systems.
Reliable, very fast and easy to use database server.
Works on client-server model.
Highly Secure and Scalable
High Performance
High productivity as it uses stored procedures, triggers, views to write a highly productive code.
Supports large databases efficiently.
Supports many operating systems like Linux*,CentOS*, Solaris*,Ubuntu*,Windows*, MacOS*,FreeBSD* and others.

Syntax help

Commands

1. CREATE

CREATE TABLE table_name (
                column1 datatype,
                column2 datatype,
                ....);

Example

CREATE TABLE EMPLOYEE (
  empId INTEGER PRIMARY KEY,
  name TEXT NOT NULL,
  dept TEXT NOT NULL
);

2. ALTER

ALTER TABLE Table_name ADD column_name datatype;

Example

INSERT INTO EMPLOYEE VALUES (0001, 'Dave', 'Sales');

3. TRUNCATE

TRUNCATE table table_name;

4. DROP

DROP TABLE table_name;

5. RENAME

RENAME TABLE table_name1 to new_table_name1;

6. COMMENT

Single-Line Comments:

 --Line1;

Multi-Line comments:

   /* Line1,
   Line2 */

DML Commands

1. INSERT

INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...);

Note: Column names are optional.

Example

INSERT INTO EMPLOYEE VALUES (0001, 'Ava', 'Sales');

2. SELECT

SELECT column1, column2, ...
FROM table_name
[where condition];

Example

SELECT * FROM EMPLOYEE where dept ='sales';

3. UPDATE

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

Example

UPDATE EMPLOYEE SET dept = 'Sales' WHERE empId='0001';

4. DELETE

DELETE FROM table_name where condition;

Example

DELETE from EMPLOYEE where empId='0001';

Indexes

1. CREATE INDEX

  CREATE INDEX index_name on table_name(column_name);

To Create Unique index:

  CREATE UNIQUE INDEX index_name on table_name(column_name);

2. DROP INDEX

DROP INDEX index_name ON table_name;

Views

1. Create a View

Creating a View:
CREATE VIEW View_name AS 
Query;

2. How to call view

SELECT * FROM View_name;

3. Altering a View

ALTER View View_name AS 
Query;

4. Deleting a View

DROP VIEW View_name;

Triggers

1. Create a Trigger

CREATE TRIGGER trigger_name trigger_time trigger_event
    ON tbl_name FOR EACH ROW [trigger_order] trigger_body
/* where
trigger_time: { BEFORE | AFTER }
trigger_event: { INSERT | UPDATE | DELETE }
trigger_order: { FOLLOWS | PRECEDES } */

2. Drop a Trigger

DROP TRIGGER [IF EXISTS] trigger_name;

Stored Procedures

1. Create a Stored Procedure

CREATE PROCEDURE sp_name(p1 datatype)
BEGIN
/*Stored procedure code*/
END;

2. How to call Stored procedure

CALL sp_name;

3. How to delete stored procedure

DROP PROCEDURE sp_name;

Joins

1. INNER JOIN

SELECT * FROM TABLE1 INNER JOIN TABLE2 where condition;

2. LEFT JOIN

SELECT * FROM TABLE1 LEFT JOIN TABLE2 ON condition;

3. RIGHT JOIN

SELECT * FROM TABLE1 RIGHT JOIN TABLE2 ON condition;

4. CROSS JOIN

SELECT select_list from TABLE1 CROSS JOIN TABLE2;