Table

Creating Table

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Altering Table

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Add Column

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-- adding column to table
ALTER TABLE [schema].[table name]
ADD COLUMN [column name] [data type];
​
-- example
ALTER TABLE public.rainfalls
ADD COLUMN is_enable boolean [CONSTRAINT];
​
-- renaming column in table
ALTER TABLE public.rainfalls
RENAME is_enable TO accurate;
​
-- add mulitple columns
ALTER TABLE rainfals
ADD COLUMN city VARCHAR(20),
ADD COLUMN pincode VARCHAR(50);
​
-- create dummy table
CREATE TABLE IF NOT EXISTS wrong_table ( name text );
-- rename table using ALTER
ALTER TABLE wrong_table RENAME TO name_table;
DROP TABLE IF EXISTS name_table;
​
-- drop column
ALTER TABLE public.rainfalls
DROP COLUMN pincode;
​
-- change data type of column
ALTER TABLE public.rainfalls
ALTER COLUMN accurate TYPE TEXT;
​
Table "public.rainfalls"
Column | Type |
----------+-----------------------+-
location | text |
year | integer |
month | integer |
raindays | integer |
accurate | TEXT |
city | character varying(20) |
​
-- altering column datatype
ALTER TABLE rainfalls
ALTER COLUMN accurate TYPE REAL
USING accurate::REAL;
​
Table "public.rainfalls"
Column | Type |
----------+-----------------------+-
location | text |
year | integer |
month | integer |
raindays | integer |
accurate | real |
city | character varying(20) |
​
​
-- set default value of column
ALTER TABLE users
ALTER COLUMN is_enable SET DEFAULT 'Y';

Delete

-- delete table
DROP TABLE IF EXISTS [table name];
​
-- delete row
DROP TABLE IF EXISTS [table name];
​
-- delete column
ALTER TABLE [table name]
DROP column [column name];
​
-- delete constraints
ALTER TABLE [table name]
DROP CONSTRAINT [constrain name];

Select

The SELECT statement has the following clauses:
  • Select distinct rows using DISTINCT operator.
  • Sort rows using ORDER BY clause.
  • Filter rows using WHERE clause.
  • Select a subset of rows from a table using LIMIT or FETCH clause.
  • Group rows into groups using GROUP BY clause.
  • Filter groups using HAVING clause.
  • Join with other tables using joins such as INNER JOIN, LEFT JOIN, FULL OUTER JOIN, CROSS JOIN clauses.
  • Perform set operations using UNION, INTERSECT, and EXCEPT.
SELECT first_name, last_name
FROM directors
LIMIT 5;
Representation
Function
ASC
Ascending
DESC
Descending
SELECT * FROM directors LIMIT 3;
​
director_id | first_name | last_name | date_of_birth | nationality
-------------+------------+-----------+---------------+-------------
1 | Tomas | Alfredson | 1965-04-01 | Swedish
2 | Paul | Anderson | 1970-06-26 | American
3 | Wes | Anderson | 1969-05-01 | American
​
SELECT * FROM directors ORBER BY date_of_birth ASC|DESC;
​
SELECT DISTINCT nationality FROM directors;
​
-- to select one column with condtion
SELECT * FROM directors WHERE nationality = 'Chinese';
​
-- Two or more conditions
SELECT
*
FROM
directors
WHERE
nationality = 'Mexican'
AND
date_of_birth='1964-10-09';

Column Alias

-- normal column aliases
SELECT
first_name || ' ' || last_name as full_name
FROM
directors LIMIT 5;
​
-- with spaces
SELECT
first_name || ' ' || last_name "full name"
FROM
customer;

Insert

CREATE TABLE IF NOT EXISTS temp_table (
col1 text,
col2 text,
);
​
INSERT INTO table (col1, col2)
VALUES ( 'VALUE 1' , 'VALUE 2');
​
-- MULTIPLE
INSERT INTO table (col1, col2)
VALUES ( 'VALUE 1' , 'VALUE 2','VALUE 3','VALUE 4');
​
-- STRING WITH QUOTES , add another ' before '
INSERT INTO table (col1)
VALUES ( 'VALUE''S 1' );
​
-- RETURNING ROWS
INSERT INTO temp_table (col1, col2)
VALUES ( 'VALUE 5' , 'VALUE 6')
RETURNING *;

Updating

UPDATE directors set last_name = 'Walker'
where director_id = 2;
​
-- returning updated row
update actors set last_name = 'Anderson'
where director_id = 150 returning *;
​
-- update all records
update [table name] set [column name] = [value];
​
UPDATE [table name]
SET email = 'not found'
WHERE
email IS NULL;

Upsert

-- syntax for upsert
INSERT INTO tablename ( col_list ) VALUES
( value_list ) ON CONFLICT (COL_NAME)
DO
NOTHING
-- OR
UPDATE SET col = val where condition;
​
-- syntax for upsert
INSERT INTO tablename ( COL_NAME ) VALUES
( value_list ) ON CONFLICT (COL_NAME)
DO
UPDATE SET COL_NAME = EXCLUDED.COL_NAME;
Last modified 7mo ago