added PostgreSQL chet sheets

sheets/_psql/columns

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+# Add column
+ALTER TABLE <table_name> IF EXISTS
+ADD <column_name> <data_type> [<constraints>];
+
+# Update column
+ALTER TABLE <table_name> IF EXISTS
+ALTER <column_name> TYPE <data_type> [<constraints>];
+
+# Delete column
+ALTER TABLE <table_name> IF EXISTS
+DROP <column_name>;
+
+# Update column to be an auto-incrementing primary key
+ALTER TABLE <table_name>
+ADD COLUMN <column_name> SERIAL PRIMARY KEY;
+
+# Insert into a table, with an auto-incrementing primary key
+INSERT INTO <table_name>
+VALUES (DEFAULT, <value1>);
+#
+INSERT INTO <table_name> (<column1_name>,<column2_name>)
+VALUES ( <value1>,<value2> );

sheets/_psql/databases

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+# Create a new database
+CREATE DATABASE [IF NOT EXISTS] db_name;
+
+# Delete a database permanently
+DROP DATABASE [IF EXISTS] db_name;

sheets/_psql/indexes

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+# Creating an index with the specified name on a table
+CREATE [UNIQUE] INDEX index_name
+ON table (column,...)
+
+# Removing a specified index from table
+DROP INDEX index_name;

sheets/_psql/performance

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+# Show the query plan for a query
+EXPLAIN query;
+
+# Show and execute the query plan for a query
+EXPLAIN ANALYZE query;
+
+# Collect statistics
+ANALYZE table_name;

sheets/_psql/permissions

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+# Grant all permissions on database
+GRANT ALL PRIVILEGES ON DATABASE <db_name> TO <user_name>;
+
+# Grant connection permissions on database
+GRANT CONNECT ON DATABASE <db_name> TO <user_name>;
+
+# Grant permissions on schema
+GRANT USAGE ON SCHEMA public TO <user_name>;
+
+# Grant permissions to functions
+GRANT EXECUTE ON ALL FUNCTIONS IN SCHEMA public TO <user_name>;
+
+# Grant permissions to select, update, insert, delete, on a all tables
+GRANT SELECT, UPDATE, INSERT ON ALL TABLES IN SCHEMA public TO <user_name>;
+
+# Grant permissions, on a table
+GRANT SELECT, UPDATE, INSERT ON <table_name> TO <user_name>;
+
+# Grant permissions, to select, on a table
+GRANT SELECT ON ALL TABLES IN SCHEMA public TO <user_name>;

sheets/_psql/roles

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+# Create a new role
+CREATE ROLE role_name;
+
+# Create a new role with a username and password:
+CREATE ROLE username NOINHERIT LOGIN PASSWORD password;
+
+# Change role for current sesion to the new_role:
+SET ROLE new_role;
+
+# Allow role_1 to set its role as role_2:
+GRANT role_2 TO role_1;

sheets/_psql/schema

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+# List schemas
+\dn
+SELECT schema_name FROM information_schema.schemata;
+SELECT nspname FROM pg_catalog.pg_namespace;
+
+# Create schema
+CREATE SCHEMA IF NOT EXISTS <schema_name>;
+
+# Drop schema
+DROP SCHEMA IF EXISTS <schema_name> CASCADE;

sheets/_psql/select

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+# Query all data from a table
+SELECT * FROM table_name;
+
+Query data from specified columns of all rows in a table
+SELECT column, column2... FROM table;
+
+# Query data and select only unique rows
+SELECT DISTINCT (column) FROM table;
+
+# Query data from a table with a filter
+SELECT * FROM table WHERE condition;
+
+# Set an alias for a column in the result set
+SELECT column_1 AS new_column_1, ...
+FROM table;
+
+# Query data using the LIKE operator
+SELECT * FROM table_name
+WHERE column LIKE '%value%'
+
+# Query data using the BETWEEN operator
+SELECT * FROM table_name
+WHERE column BETWEEN low AND high;
+
+# Query data using the IN operator
+SELECT * FROM table_name
+WHERE column IN (value1, value2,...);
+
+# Constrain the returned rows with LIMIT clause
+SELECT * FROM table_name
+LIMIT limit OFFSET offset
+ORDER BY column_name;
+
+# Query data from multiple using the inner join, left join, full outer join, cross join and natural join:
+SELECT * FROM table1 INNER JOIN table2 ON conditions
+SELECT * FROM table1 LEFT JOIN table2 ON conditions
+SELECT * FROM table1 FULL OUTER JOIN table2 ON conditions
+SELECT * FROM table1 CROSS JOIN table2;
+SELECT * FROM table1 NATURAL JOIN table2;
+
+# Return the number of rows of a table.
+SELECT COUNT (*)
+FROM table_name;
+
+# Sort rows in ascending or descending order
+SELECT column, column2, ...
+FROM table
+ORDER BY column ASC [DESC], column2 ASC [DESC],...;
+
+# Group rows using GROUP BY clause.
+SELECT *
+FROM table
+GROUP BY column_1, column_2, ...;
+
+# Filter groups using the HAVING clause.
+SELECT *
+FROM table
+GROUP BY column_1
+HAVING condition;
+
+# Combine the result set of two or more queries with UNION operator:
+SELECT * FROM table1
+UNION
+SELECT * FROM table2;
+
+# Minus a result set using EXCEPT operator:
+SELECT * FROM table1
+EXCEPT
+SELECT * FROM table2;
+
+# Get intersection of the result sets of two queries:
+SELECT * FROM table1
+INTERSECT
+SELECT * FROM table2;

sheets/_psql/shell

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+# Connect to a specific database
+\c database_name
+
+# To quite the psql
+\q
+
+# List all databases in the PostgreSQL database server
+\l
+
+# List all schemas
+\dn
+
+# List all stored procedures and functions
+\df
+
+# List all views
+\dv
+
+# Lists all tables in a current database
+\dt
+
+# Get more information on tables in the current database
+\dt+
+
+# Get detailed information on a table
+\d+ table_name
+
+# Show a stored procedure or function code
+\df+ function_name
+
+# Show query output in the pretty-format
+\x
+
+# List all users
+\du
+
+# Export table into CSV file
+\copy <table_name> TO '<file_path>' CSV
+
+# Export table, only specific columns, to CSV file
+\copy <table_name>(<column_1>,<column_1>,<column_1>) TO '<file_path>' CSV
+
+# Import CSV file into table
+\copy <table_name> FROM '<file_path>' CSV
+
+# Import CSV file into table, only specific columns
+\copy <table_name>(<column_1>,<column_1>,<column_1>) FROM '<file_path>' CSV
+

sheets/_psql/tables

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+# Create a new table or a temporary table
+CREATE [TEMP] TABLE [IF NOT EXISTS] table_name(
+   pk SERIAL PRIMARY KEY,
+   c1 type(size) NOT NULL,
+   c2 type(size) NULL,
+   ...
+);
+
+# Add a new column into a table
+ALTER TABLE table_name ADD COLUMN new_column_name TYPE;
+
+# Drop a column in a table
+ALTER TABLE table_name DROP COLUMN column_name;
+
+# Rename a column
+ALTER TABLE table_name RENAME column_name TO new_column_name;
+
+# Set or remove a default value for a column
+ALTER TABLE table_name ALTER COLUMN [SET DEFAULT value | DROP DEFAULT]
+
+# Add a primary key to a table
+ALTER TABLE table_name ADD PRIMARY KEY (column,...);
+
+# Remove the primary key from a table
+ALTER TABLE table_name 
+DROP CONSTRAINT primary_key_constraint_name;
+
+# Rename a table
+ALTER TABLE table_name RENAME TO new_table_name;
+
+# Drop a table and its dependent objects:
+DROP TABLE [IF EXISTS] table_name CASCADE;

sheets/_psql/update

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+# Insert a new row into a table
+INSERT INTO table(column1,column2,...)
+VALUES(value_1,value_2,...);
+
+# Insert multiple rows into a table
+INSERT INTO table_name(column1,column2,...)
+VALUES(value_1,value_2,...),
+      (value_1,value_2,...),
+      (value_1,value_2,...)...
+
+# Update data for all rows
+UPDATE table_name
+SET column_1 = value_1,
+    ...;
+
+# Update data for a set of rows specified by a condition in WHERE clause
+UPDATE table
+SET column_1 = value_1,
+    ...
+WHERE condition;
+
+# Delete all rows of a table
+DELETE FROM table_name;
+
+# Delete specific rows based on a condition
+DELETE FROM table_name
+WHERE condition;

sheets/_psql/users

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+# List roles
+SELECT rolname FROM pg_roles;
+
+# Create user
+CREATE USER <user_name> WITH PASSWORD '<password>';
+
+# Drop user
+DROP USER IF EXISTS <user_name>;
+
+# Alter user password
+ALTER ROLE <user_name> WITH PASSWORD '<password>';

sheets/_psql/views

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+# Create a view
+CREATE OR REPLACE view_name AS
+query;
+
+# Create a recurisve view:
+CREATE RECURSIVE VIEW view_name(columns) AS
+SELECT columns;
+
+# Create a materialized view:
+CREATE MATERIALIZED VIEW view_name
+AS
+query
+WITH [NO] DATA;
+
+# Refresh a materialized view
+REFRESH MATERIALIZED VIEW CONCURRENTLY view_name;
+
+# Drop a view
+DROP VIEW [ IF EXISTS ] view_name;
+
+# Drop a materialized view
+DROP MATERIALIZED VIEW view_name;
+
+# Rename a view
+ALTER VIEW view_name RENAME TO new_name;

sheets/pg_top

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+# pg_top
+# Display and update information about the top cpu PostgreSQL processes 
+
+# connect to port 5432 using user postgres, and database, ask for password
+pg_top -p 5432 -U postgres -d database -W
+
+# Interactive mode keys:
+#
+#  A
+#      Display the actual query plan (EXPLAIN ANALYZE)
+#  E
+#      Display re-determined execution plan (EXPLAIN) of the SQL statement by a backend process
+#  L
+#      Display the currently held locks by a backend process
+#  Q
+#      Display the currently running query of a backend process
+#  X
+#      Display user index statistics.