Tag: Database Cheat Sheet

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

Insert one row into a table

INSERT INTO t(column_list)
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;

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
);

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;

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

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;