notes/Databases/SurrealDB/Syntax.md

## Syntax

- [CREATE](https://docs.surrealdb.com/docs/surrealql/statements/select): Creates resources/records, similar to `INSERT INTO` in Postgres
- [DEFINE](https://docs.surrealdb.com/docs/surrealql/statements/define/overview): Creates namespaces, databases, and scopes, logins
- [UPDATE](https://docs.surrealdb.com/docs/surrealql/statements/update): Updates resources/records, similar to `UPDATE table_name SET ...` in Postgres
- [DELETE](https://docs.surrealdb.com/docs/surrealql/statements/delete): Deletes resources/records, similar to `DELETE` in Postgres
- [USE](https://docs.surrealdb.com/docs/surrealql/statements/use/): Used for switching in between namespaces and databases
- `SLEEP`: Used to make the database go to sleep
- `BEGIN`: Used for making a group of SurrealQL statements a singular transaction. Transaction block must end with a `COMMIT`
- `COMMIT`: Used for making a group of SurrealQL statements a singular transaction. Transaction block must start with a `BEGIN`
- [RELATE](https://docs.surrealdb.com/docs/surrealql/statements/use/): Used to traverse records efficiently without the need for SQL JOINs


## Examples

### Basic `SELECT` examples

```sql
-- Select all fields from a table
SELECT * FROM person;

-- Select specific fields from a table
SELECT name, address, email FROM person;

-- Select all fields from a specific record
SELECT * FROM person:tobie;

-- Select specific fields from a specific record
SELECT name, address, email FROM person:tobie;

-- Alias/rename fields
SELECT name AS user_name, address FROM person;

-- Select just a single record
-- Using the ONLY keyword, just an object for the record in question will be returned.
-- This, instead of an array with a single object.
SELECT * FROM ONLY person:john;
```

#### Examples
###### Rust

### Advanced `SELECT` expressions

```SQL
-- Select nested objects/values
SELECT address.city FROM person;

-- Select all nested array values
-- note the .* syntax works to select everything from an array or object-like values
SELECT address.*.coordinates AS coordinates FROM person;
-- Equivalent to 
SELECT address.coordinates AS coordinates FROM person;

-- Select one item from an array
SELECT address.coordinates[0] AS latitude FROM person;

-- Select unique values from an array
SELECT array::distinct(tags) FROM article;

-- Select unique values from a nested array across an entire table
SELECT array::group(tags) AS tags FROM article GROUP ALL;

-- Use mathematical calculations in a select expression
SELECT ( ( celsius * 2 ) + 30 ) AS fahrenheit FROM temperature;

-- Return boolean expressions with an alias
SELECT rating >= 4 as positive FROM review;

-- Select manually generated object structure
SELECT { weekly: false, monthly: true } AS `marketing settings` FROM user;

-- Select filtered nested array values
SELECT address[WHERE active = true] FROM person;

-- Select a person who has reacted to a post using a celebration
-- You can see the graph as: person->(reacted_to WHERE type='celebrate')->post
SELECT * FROM person WHERE ->(reacted_to WHERE type='celebrate')->post;

-- Select a remote field from connected out graph edges
SELECT ->likes->friend.name AS friends FROM person:tobie;

-- Use the result of a subquery as a returned field
SELECT *, (SELECT * FROM events WHERE type = 'activity' LIMIT 5) AS history FROM user;
```

### Multiple targets with `FROM`

```SQL
-- This command selects all records from both 'user' and 'admin' tables.
SELECT * FROM user, admin;

-- This command selects all records from the table named in the variable '$table',
-- but only if the 'admin' field of those records is true.
-- This query is equivalent to 'SELECT * FROM user WHERE admin = true'.
LET $table = "user";
SELECT * FROM type::table($table) WHERE admin = true;

-- This command selects a single record from:
-- * the table named in the variable '$table',
-- * and the identifier named in the variable '$id'.
-- This query is equivalent to 'SELECT * FROM user:admin'.
LET $table = "user";
LET $id = "admin";
SELECT * FROM type::thing($table, $id);
```
### `UPDATE` examples

```SQL
-- Update all records in a table
UPDATE person SET skills += ['breathing'];

-- Update or create a record with a specific numeric id
UPDATE person:100 SET name = 'Tobie', company = 'SurrealDB', skills = ['Rust', 'Go', 'JavaScript'];

-- Update or create a record with a specific string id
UPDATE person:tobie SET name = 'Tobie', company = 'SurrealDB', skills = ['Rust', 'Go', 'JavaScript'];

-- Update just a single record
-- Using the ONLY keyword, just an object for the record in question will be returned.
-- This, instead of an array with a single object.
UPDATE ONLY person:tobie SET name = 'Tobie', company = 'SurrealDB', skills = ['Rust', 'Go', 'JavaScript'];
```

### Logins
Create a login table
```sql
DEFINE TABLE user SCHEMAFULL PERMISSIONS FOR select, update, delete WHERE id = $auth.id;

DEFINE FIELD name ON user TYPE string ASSERT string::len($value) >= 2;

DEFINE FIELD username ON user TYPE string VALUE string::lowercase($value);

DEFINE FIELD password ON user TYPE string PERMISSIONS FOR select NONE;

DEFINE SCOPE user SESSION 7d SIGNIN ( SELECT * FROM user WHERE username = $username AND crypto::argon2::compare(password, $password) ) SIGNUP ( CREATE user CONTENT { name: $name, username: $username, password: crypto::argon2::generate($password) } );
```