Ecosyste.ms: Awesome
An open API service indexing awesome lists of open source software.
https://github.com/amadr-95/sql-advanced
https://github.com/amadr-95/sql-advanced
database-indexes database-management database-transactions plpgsql postgresql sql
Last synced: 3 days ago
JSON representation
- Host: GitHub
- URL: https://github.com/amadr-95/sql-advanced
- Owner: amadr-95
- Created: 2024-04-25T16:13:41.000Z (9 months ago)
- Default Branch: master
- Last Pushed: 2024-04-25T16:17:49.000Z (9 months ago)
- Last Synced: 2024-11-18T05:30:12.275Z (about 2 months ago)
- Topics: database-indexes, database-management, database-transactions, plpgsql, postgresql, sql
- Language: PLpgSQL
- Homepage:
- Size: 223 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# [ADVANCED DATABASES](https://www.amigoscode.com/courses/advanced-databases)
## JOINS
### - (INNER) JOIN
```
Select records that have matching values in both tables
```
### - (OUTER) LEFT JOIN
```
Select records from the left table with matching right table records
```
### - (OUTER) RIGHT JOIN
```
Select records from the right table with matching left table records
```
### - FULL JOIN
```
Select all records that match either left or right table records
```
## TRANSACTIONS (A.C.I.D. PRINCIPLES)
```
1. ATOMICITY:
- Atomicity ensures that a transaction is performed completely or not performed at all.
- If any part of the transaction fails, the entire transaction is rolled back to its previous state.
- It guarantees that data remains consistent even in cases of failure.
2. CONSISTENCY:
- Consistency ensures that only changes to data that respect all system integrity constraints are made.
- Before and after a transaction, data must be in a valid state.
3. ISOLATION:
- Isolation principle ensures that the effects of a transaction are not visible to other transactions until it is completely finished.
- Transactions are executed in isolation from one another, preventing operations in one transaction from interfering with concurrent transactions.
4. DURABILITY:
- Durability guarantees that once a transaction is successfully completed and committed, the changes will persist even in the event of a system failure.
- Data modified by the transaction is permanently saved and will not be lost, even in system failure situations.
```
### BEGIN, COMMIT, ROLLBACK
- **Begin**: starts a transaction
- **Commit**: commits a transaction
- **Rollback**: reverts the data to its previous state if anything goes wrong
## INDEXES
Using indexes may **increases the performance** when retriving many rows.
- **View indexes**
```sql
SELECT tablename, indexname, indexdef FROM pg_indexes WHERE schemaname = 'public';
```
- **Create indexes**
```sql
CREATE INDEX table_colum_name_idx ON table(column_name);
```
- **Delete indexes**
```sql
DROP INDEX index_name;
```
### Multi-column indexes
Combining two or more columns.
```sql
CREATE INDEX table_column1_column2_idx ON table(column1, column2);
```
```
... WHERE column1 = '' AND column2 = '' ✅
... WHERE column1 = '' ✅
... WHERE column2 = '' ❌ (index does not have any effect)
```
### Unique indexes
```sql
CREATE UNIQUE INDEX table_column_name_unique_idx
ON table(column_name);
```
### Partial indexes
```sql
CREATE UNIQUE INDEX table_column_name_partial_idx
ON table(column_name)
WHERE column_name = condition (boolean for example)
```
## FUNCTIONS
- Create functions
```sql
CREATE OR REPLACE FUNCTION function_name(param1 TYPE, param2 TYPE...)
RETURNS TYPE
LANGUAGE plpgsql
AS
$$
DECLARE
--variable declaration
variable_name TYPE;
BEGIN
--logic
RETURN variable_name;
END;
$$;
```
- Use functions
```sql
SELECT function_name(param1, param2, ...);
```
- View functions in terminal
```bash
\df
```
- Delete functions
```sql
DROP FUNCTION function_name;
```
## ROLES
- View roles in terminal
```bash
\du
```
- Create role (rol = user)
```sql
CREATE ROLE/USER name; --basic
```
```sql
CREATE ROLE/USER name (WITH) LOGIN PASSWORD 'password';
```
- Modify role
```sql
ALTER ROLE rol_name [options]
```
Options:
- SUPERUSER | NOSUPERUSER
- CREATEDB | NOCREATEDB
- CREATEROLE | NOCREATEROLE
- INHERIT | NOINHERIT
- LOGIN | NOLOGIN
- REPLICATION | NOREPLICATION
- BYPASSRLS | NOBYPASSRLS
- CONNECTION LIMIT limit
- PASSWORD 'password' | PASSWORD NULL
- VALID UNTIL 'timestamp'
- Delete role
```sql
DROP ROLE name;
```
### Privileges
#### Grant
```sql
GRANT privilege_list | ALL
ON table_name | ALL TABLES IN SCHEMA schema_name
TO role_name;
```
Privileges:
- SELECT
- INSERT
- UPDATE
- DELETE
- TRUNCATE
- ...
#### Revoke
```sql
REVOKE privilege_list | ALL
ON table_name | ALL TABLES IN SCHEMA schema_name
FROM role_name;
```
## SCHEMAS
- View schemas
```bash
\dn
```
```sql
SELECT current_schema(); --public by default
```
- Create schema
```sql
CREATE SCHEMA schema_name;
```
- Create tables in custom schemas
```sql
CREATE TABLE schema_name.table_name;
```
### Search path
```sql
SHOW search_path;
```
- Change the default search path
```sql
SET search_path TO new_schema, default_schema (public);
```
## BACKUP AND RESTORE DATABASES
### Backup
```bash
pg_dump --help //see all options
```
- Dump a database
```bash
pg_dump -U username -d db_name -F format_file -f path/file_name.sql
```
- Dump all databases
```bash
pg_dumpall -U username -f path/file_name.sql
```
### Restore
```bash
pg_restore --help //see all options
```
- Using psql (.sql files)
```bash
psql -U username -d db_name -f path/backup_file_name.sql
```
- Using pg_restore (.tar files)
```bash
pg_restore -U username -d db_name path/backup_file_name.tar
```