MySQL Tutorial - MySQL By Examples for Beginners

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Learn MySql Tutorial

This cheat sheet incorporates image language structure and strategies to help you utilizing MySQL. MySQL is an information base administration framework. It could be anything from a straightforward shopping rundown to an image display or the immense measures of data in a corporate organization. To add, access, and cycle information put away in a PC data set, you need a data set administration framework like MySQL Server.

MySQL: Commands Cheat Sheet

To login (from unix shell) use -h only if needed.

[mysql dir]/bin/mysql -h hostname -u root -p

Create a database on the sql server.

create database [databasename];

List all databases on the sql server.

show databases;

Switch to a database.

use [db name];

To see all the tables in the db.

show tables;

To see database’s field formats.

describe [table name];

To delete a db.

drop database [database name];

To delete a table.

drop table [table name];

Managing Triggers

Create or modify a trigger

CREATE OR MODIFY TRIGGER trigger_name
WHEN EVENT
ON table_name TRIGGER_TYPE
EXECUTE stored_procedure;

Create a trigger invoked before a new row is inserted into the person table

WHEN
  BEFORE – invoke before the event occurs
  AFTER – invoke after the event occurs
EVENT
  INSERT – invoke for INSERT
  UPDATE – invoke for UPDATE
  DELETE – invoke for DELETE
TRIGGER_TYPE
  FOR EACH ROW
  FOR EACH STATEMENT
CREATE TRIGGER before_insert_person
BEFORE INSERT
ON person FOR EACH ROW
EXECUTE stored_procedure;

Delete a specific trigger

DROP TRIGGER trigger_name

SQL Aggregate: Functuions Cheat Sheet

AVG returns the average of a list

COUNT returns the number of elements of a list

SUM returns the total of a list

MAX returns the maximum value in a list

MIN returns the minimum value in a list

Managing Indexes

Create an index on c1 and c2 of the table t

CREATE INDEX idx_name
ON t(c1,c2);

Create a unique index on c3, c4 of the table t

CREATE UNIQUE INDEX idx_name
ON t(c3,c4);

Drop an index

DROP INDEX idx_name;

VALUES(value_list);

Insert multiple rows into a table

INSERT INTO t(column_list)
VALUES (value_list),
(value_list), ….;

Insert rows from t2 into t1

INSERT INTO t1(column_list)
SELECT column_list
FROM t2;

Update values in the column c1, c2 that match
the condition

UPDATE t
SET c1 = new_value,
c2 = new_value
WHERE condition;

Delete all data in a table

DELETE FROM t;

Delete subset of rows in a table

DELETE FROM t
WHERE condition;

Using SQL Constraints

Set c1 and c2 as a primary key

CREATE TABLE t(
c1 INT, c2 INT, c3 VARCHAR,
PRIMARY KEY (c1,c2)
);

Set c2 column as a foreign key

CREATE TABLE t1(
c1 INT PRIMARY KEY,
c2 INT,
FOREIGN KEY (c2) REFERENCES t2(c2)
);

Make the values in c1 and c2 unique

CREATE TABLE t(
c1 INT, c1 INT,
UNIQUE(c2,c3)
);

Ensure c1 > 0 and values in c1 >= c2

CREATE TABLE t(
c1 INT, c2 INT,
CHECK(c1> 0 AND c1 >= c2)
);

Set values in c2 column not NULL

CREATE TABLE t(
c1 INT PRIMARY KEY,
c2 VARCHAR NOT NULL
);

Managing Tables

Create a new table with three columns

CREATE TABLE t (
id INT PRIMARY KEY,
name VARCHAR NOT NULL,
price INT DEFAULT 0
);

Delete the table from the database

DROP TABLE t ;

Add a new column to the table

ALTER TABLE t ADD column;

Drop column c from the table

ALTER TABLE t DROP COLUMN c ;

Add a constraint

ALTER TABLE t ADD constraint;

Drop a constraint

ALTER TABLE t DROP constraint;

Rename a table from t1 to t2

ALTER TABLE t1 RENAME TO t2

Rename column c1 to c2

ALTER TABLE t1 RENAME c1 TO c2 ;

Remove all data in a table

TRUNCATE TABLE t;

Using SQL Operators

Combine rows from two queries

SELECT c1, c2 FROM t1
UNION [ALL]
SELECT c1, c2 FROM t2;

Return the intersection of two queries

SELECT c1, c2 FROM t1
INTERSECT
SELECT c1, c2 FROM t2;

Subtract a result set from another result set

SELECT c1, c2 FROM t1
MINUS
SELECT c1, c2 FROM t2;

Query rows using pattern matching %, _

SELECT c1, c2 FROM t1
WHERE c1 [NOT] LIKE pattern;

Query rows in a list

SELECT c1, c2 FROM t
WHERE c1 [NOT] IN value_list;

Query rows between two values

SELECT c1, c2 FROM t
WHERE c1 BETWEEN low AND high;

Check if values in a table is NULL or not

SELECT c1, c2 FROM t
WHERE c1 IS [NOT] NULL;

Managing Views

Create a new view that consists of c1 and c2

CREATE VIEW v(c1,c2)
AS
SELECT c1, c2
FROM t;

Create a new view with check option

CREATE VIEW v(c1,c2)
AS
SELECT c1, c2
FROM t;
WITH [CASCADED | LOCAL] CHECK OPTION;

Create a recursive view

CREATE RECURSIVE VIEW v
AS
select-statement -- anchor part
UNION [ALL]
select-statement; -- recursive part

Create a temporary view

CREATE TEMPORARY VIEW v
AS
SELECT c1, c2
FROM t;

Delete a view

DROP VIEW view_name

Querying data from multiple tables

Inner join t1 and t2

SELECT c1, c2
FROM t1
INNER JOIN t2 ON condition;

Left join t1 and t1

SELECT c1, c2
FROM t1
LEFT JOIN t2 ON condition;

Perform full outer join

SELECT c1, c2
FROM t1
FULL OUTER JOIN t2 ON condition;

Produce a Cartesian product of rows in tables

SELECT c1, c2
FROM t1
CROSS JOIN t2;

Join t1 to itself using INNER JOIN clause

SELECT c1, c2
FROM t1 A
INNER JOIN t2 B ON condition;

Querying Data From Table

Query data in columns c1, c2 from a table

SELECT c1, c2 FROM t;

Query all rows and columns from a table

SELECT * FROM t;

Query data and filter rows with a condition

SELECT c1, c2 FROM t
WHERE condition;

Query distinct rows from a table

SELECT DISTINCT c1 FROM t
WHERE condition;

Group rows using an aggregate function

SELECT c1, aggregate(c2)
FROM t
GROUP BY c1;

Filter groups using HAVING clause

SELECT c1, aggregate(c2)
FROM t
GROUP BY c1
HAVING condition;

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