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4
technology/dev/programming/languages/Rust.md
View file

@ -79,7 +79,7 @@ Conditionals like `if` and `match` can be used, while `match` can do more powerf
let age = 20;
if age > 18 {
println!("Adult");
} else if age == 18 {
} else if age == 18 {
println!("Exactly 18");
} else {
println!("Minor");
@ -156,7 +156,7 @@ struct Person {
impl Person {
fn new(first_name: &str) -> Self {
Self {
Self {
first_name: first_name.to_string(),
age: 0
}

280
technology/dev/programming/languages/SQL.md
View file

@ -10,7 +10,7 @@ A database most often contains one or more tables. Each table is identified by a
Most of the actions you need to perform on a database are done with SQL statements.
Example:
```sql
SELECT * FROM Customers;
SELECT * FROM Customers;
```
### Comments
@ -31,12 +31,12 @@ SELECT * FROM Customers;
```
## SELECT
The `SELECT` statement is used to select data from a database.
The `SELECT` statement is used to select data from a database.
Select:
```sql
SELECT column1, column2, ...
FROM table_name;
SELECT column1, column2, ...
FROM table_name;
```
Select all:
@ -45,7 +45,7 @@ SELECT * FROM table
```
### SELECT DISTINC
The `SELECT DISTINCT` statement is used to return only distinct (different) values.
The `SELECT DISTINCT` statement is used to return only distinct (different) values.
```sql
SELECT DISTINCT Country FROM Customers;
@ -53,7 +53,7 @@ SELECT COUNT(DISTINCT Country) FROM Customers;
```
## WHERE
The `WHERE` clause is used to filter records.
The `WHERE` clause is used to filter records.
```sql
SELECT column1, column2, ...
@ -71,7 +71,7 @@ SELECT * FROM Customers
WHERE CustomerID=1;
```
The following operators can be used in the `WHERE` clause:
The following operators can be used in the `WHERE` clause:
| Operator | Description |
| -------- | ------------------------------------------------------------------------------- |
@ -80,17 +80,17 @@ The following operators can be used in the `WHERE` clause:
| < | Less than |
| >= | Greater than or equal |
| <= | Less than or equal |
| <> | Not equal. **Note:** In some versions of SQL this operator may be written as != |
| <> | Not equal. **Note:** In some versions of SQL this operator may be written as != |
| BETWEEN | Between a certain range |
| LIKE | Search for a pattern |
| IN | To specify multiple possible values for a column |
### LIKE
The `LIKE` operator is used in a `WHERE` clause to search for a specified pattern in a column.
The `LIKE` operator is used in a `WHERE` clause to search for a specified pattern in a column.
There are two wildcards often used in conjunction with the `LIKE` operator:
-  The percent sign `%` represents zero, one, or multiple characters
-  The underscore sign `_` represents one, single character
There are two wildcards often used in conjunction with the `LIKE` operator:
- The percent sign `%` represents zero, one, or multiple characters
- The underscore sign `_` represents one, single character
```sql
SELECT column1, column2, ...
@ -99,72 +99,72 @@ WHERE columnN LIKE pattern;
```
#### The _ Wildcard
The `_` wildcard represents a single character.
It can be any character or number, but each `_` represents one, and only one, character.
The `_` wildcard represents a single character.
It can be any character or number, but each `_` represents one, and only one, character.
```sql
SELECT * FROM Customers
WHERE city LIKE 'L_nd__';
SELECT * FROM Customers
WHERE city LIKE 'L_nd__';
```
#### The % Wildcard
The `%` wildcard represents any number of characters, even zero characters.
The `%` wildcard represents any number of characters, even zero characters.
```sql
SELECT * FROM Customers
WHERE city LIKE '%L%';
SELECT * FROM Customers
WHERE city LIKE '%L%';
```
#### Starts With
```sql
SELECT * FROM Customers
WHERE CustomerName LIKE 'La%';
SELECT * FROM Customers
WHERE CustomerName LIKE 'La%';
```
#### Ends With
```sql
SELECT * FROM Customers
WHERE CustomerName LIKE '%a';
SELECT * FROM Customers
WHERE CustomerName LIKE '%a';
```
#### Contains
```sql
SELECT * FROM Customers
WHERE CustomerName LIKE '%or%';
SELECT * FROM Customers
WHERE CustomerName LIKE '%or%';
```
### IN
The `IN` operator allows you to specify multiple values in a `WHERE` clause.
The `IN` operator allows you to specify multiple values in a `WHERE` clause.
The `IN` operator is a shorthand for multiple `OR` conditions.
The `IN` operator is a shorthand for multiple `OR` conditions.
```sql
SELECT * FROM Customers
WHERE Country IN ('Germany', 'France', 'UK');
SELECT * FROM Customers
WHERE Country IN ('Germany', 'France', 'UK');
```
Subquery:
```sql
SELECT * FROM Customers
WHERE CustomerID NOT IN (SELECT CustomerID FROM Orders);
SELECT * FROM Customers
WHERE CustomerID NOT IN (SELECT CustomerID FROM Orders);
```
### BETWEEN
The `BETWEEN` operator selects values within a given range. The values can be numbers, text, or dates.
The `BETWEEN` operator selects values within a given range. The values can be numbers, text, or dates.
The `BETWEEN` operator is inclusive: begin and end values are included.
The `BETWEEN` operator is inclusive: begin and end values are included.
```sql
SELECT column_name(s)
FROM table_name
WHERE column_name BETWEEN value1 AND value2;
SELECT * FROM Orders
WHERE OrderDate BETWEEN '1996-07-01' AND '1996-07-31';
SELECT * FROM Orders
WHERE OrderDate BETWEEN '1996-07-01' AND '1996-07-31';
```
### AND
The `WHERE` clause can contain one or many `AND` operators.
The `WHERE` clause can contain one or many `AND` operators.
```sql
SELECT *
@ -173,7 +173,7 @@ WHERE Country = 'Spain' AND CustomerName LIKE 'G%';
```
### OR
The `WHERE` clause can contain one or more `OR` operators.
The `WHERE` clause can contain one or more `OR` operators.
```sql
SELECT *
@ -188,20 +188,20 @@ WHERE Country = 'Spain' AND (CustomerName LIKE 'G%' OR CustomerName LIKE 'R%');
```
### NOT
The `NOT` operator is used in combination with other operators to give the opposite result, also called the negative result.
The `NOT` operator is used in combination with other operators to give the opposite result, also called the negative result.
```sql
SELECT * FROM Customers
WHERE NOT Country = 'Spain';
SELECT * FROM Customers
WHERE NOT Country = 'Spain';
SELECT * FROM Customers
WHERE City NOT IN ('Paris', 'London');
SELECT * FROM Customers
WHERE City NOT IN ('Paris', 'London');
```
## ORDER BY
The `ORDER BY` keyword is used to sort the result-set in ascending or descending order.
The `ORDER BY` keyword is used to sort the result-set in ascending or descending order.
The `ORDER BY` keyword sorts the records in ascending order by default. To sort the records in descending order, use the `DESC` keyword.
The `ORDER BY` keyword sorts the records in ascending order by default. To sort the records in descending order, use the `DESC` keyword.
```sql
SELECT column1, column2, ...
@ -210,7 +210,7 @@ ORDER BY column1, column2, ... ASC|DESC;
```
## INSERT INTO
The `INSERT INTO` statement is used to insert new records in a table.
The `INSERT INTO` statement is used to insert new records in a table.
Example:
```sql
@ -228,7 +228,7 @@ VALUES
```
## UPDATE
The `UPDATE` statement is used to modify the existing records in a table.
The `UPDATE` statement is used to modify the existing records in a table.
```sql
UPDATE table_name
@ -237,7 +237,7 @@ WHERE condition;
```
## DELETE
The `DELETE` statement is used to delete existing records in a table.
The `DELETE` statement is used to delete existing records in a table.
Example:
```sql
@ -251,11 +251,11 @@ DELETE FROM table_name;
Delete Table:
```sql
DROP TABLE table_name;
DROP TABLE table_name;
```
## LIMIT
The `LIMIT` clause is used to specify the number of records to return.
The `LIMIT` clause is used to specify the number of records to return.
```sql
SELECT * FROM Customers
@ -266,7 +266,7 @@ LIMIT 3;
SQL aliases are used to give a table, or a column in a table, a temporary name.
Aliases are often used to make column names more readable.
An alias only exists for the duration of that query.
An alias is created with the `AS` keyword.
An alias is created with the `AS` keyword.
```sql
SELECT column_name AS alias_name
@ -274,34 +274,34 @@ FROM table_name;
```
## JOIN
A `JOIN` clause is used to combine rows from two or more tables, based on a related column between them.
A `JOIN` clause is used to combine rows from two or more tables, based on a related column between them.
### INNER JOIN
The `INNER JOIN` keyword selects records that have matching values in both tables.
The `INNER JOIN` keyword selects records that have matching values in both tables.
```sql
SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;
SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;
```
# Database
## Create Database
The `CREATE DATABASE` statement is used to create a new SQL database.
The `CREATE DATABASE` statement is used to create a new SQL database.
```sql
CREATE DATABASE databasename;
```
## Delete Database
The `DROP DATABASE` statement is used to drop an existing SQL database.
The `DROP DATABASE` statement is used to drop an existing SQL database.
```sql
DROP DATABASE databasename;
```
## Create Table
The `CREATE TABLE` statement is used to create a new table in a database.
The `CREATE TABLE` statement is used to create a new table in a database.
```sql
CREATE TABLE table_name (
@ -321,15 +321,15 @@ CREATE TABLE Persons (
```
## Delete Table
The `DROP TABLE` statement is used to drop an existing table in a database.
The `DROP TABLE` statement is used to drop an existing table in a database.
```sql
DROP TABLE table_name;
```
## Change Table
The `ALTER TABLE` statement is used to add, delete, or modify columns in an existing table.
The `ALTER TABLE` statement is also used to add and drop various constraints on an existing table.
The `ALTER TABLE` statement is used to add, delete, or modify columns in an existing table.
The `ALTER TABLE` statement is also used to add and drop various constraints on an existing table.
Add Column:
```sql
@ -339,8 +339,8 @@ ADD Email varchar(255);
Drop Column:
```sql
ALTER TABLE Customers
DROP COLUMN Email;
ALTER TABLE Customers
DROP COLUMN Email;
```
Rename Column:
@ -356,7 +356,7 @@ ALTER COLUMN DateOfBirth year;
```
## Constraints
Constraints can be specified when the table is created with the `CREATE TABLE` statement, or after the table is created with the `ALTER TABLE` statement.
Constraints can be specified when the table is created with the `CREATE TABLE` statement, or after the table is created with the `ALTER TABLE` statement.
```sql
CREATE TABLE table_name (
@ -371,30 +371,30 @@ The following constraints are commonly used in SQL:
### NOT NULL
By default, a column can hold NULL values.
The `NOT NULL` constraint enforces a column to NOT accept NULL values.
The `NOT NULL` constraint enforces a column to NOT accept NULL values.
This enforces a field to always contain a value, which means that you cannot insert a new record, or update a record without adding a value to this field.
```sql
CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255) NOT NULL,
    Age int
CREATE TABLE Persons (
ID int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255) NOT NULL,
Age int
);
```
### UNIQUE
The `UNIQUE` constraint ensures that all values in a column are different.
The `UNIQUE` constraint ensures that all values in a column are different.
Both the `UNIQUE` and `PRIMARY KEY` constraints provide a guarantee for uniqueness for a column or set of columns.
Both the `UNIQUE` and `PRIMARY KEY` constraints provide a guarantee for uniqueness for a column or set of columns.
A `PRIMARY KEY` constraint automatically has a `UNIQUE` constraint.
A `PRIMARY KEY` constraint automatically has a `UNIQUE` constraint.
However, you can have many `UNIQUE` constraints per table, but only one `PRIMARY KEY` constraint per table.
However, you can have many `UNIQUE` constraints per table, but only one `PRIMARY KEY` constraint per table.
### PRIMARY KEY
The `PRIMARY KEY` constraint uniquely identifies each record in a table.
The `PRIMARY KEY` constraint uniquely identifies each record in a table.
Primary keys must contain UNIQUE values, and cannot contain NULL values.
@ -411,9 +411,9 @@ CREATE TABLE Persons (
```
### FOREIGN KEY
The `FOREIGN KEY` constraint is used to prevent actions that would destroy links between tables.
The `FOREIGN KEY` constraint is used to prevent actions that would destroy links between tables.
A `FOREIGN KEY` is a field (or collection of fields) in one table, that refers to the `PRIMARY KEY` in another table.
A `FOREIGN KEY` is a field (or collection of fields) in one table, that refers to the `PRIMARY KEY` in another table.
The table with the foreign key is called the child table, and the table with the primary key is called the referenced or parent table.
@ -428,32 +428,32 @@ CREATE TABLE Orders (
```
### CHECK
The `CHECK` constraint is used to limit the value range that can be placed in a column.
The `CHECK` constraint is used to limit the value range that can be placed in a column.
If you define a `CHECK` constraint on a column it will allow only certain values for this column.
If you define a `CHECK` constraint on a column it will allow only certain values for this column.
If you define a `CHECK` constraint on a table it can limit the values in certain columns based on values in other columns in the row.
If you define a `CHECK` constraint on a table it can limit the values in certain columns based on values in other columns in the row.
```sql
CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    CHECK (Age>=18)
CREATE TABLE Persons (
ID int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int,
CHECK (Age>=18)
);
```
### DEFAULT
The `DEFAULT` constraint is used to set a default value for a column.
The `DEFAULT` constraint is used to set a default value for a column.
The default value will be added to all new records, if no other value is specified.
```sql
CREATE TABLE Orders (
    ID int NOT NULL,
    OrderNumber int NOT NULL,
    OrderDate date DEFAULT GETDATE()
CREATE TABLE Orders (
ID int NOT NULL,
OrderNumber int NOT NULL,
OrderDate date DEFAULT GETDATE()
);
```
@ -463,17 +463,17 @@ Auto-increment allows a unique number to be generated automatically when a new r
Often this is the primary key field that we would like to be created automatically every time a new record is inserted.
```sql
CREATE TABLE Persons (
    Personid int NOT NULL AUTO_INCREMENT,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    PRIMARY KEY (Personid)
CREATE TABLE Persons (
Personid int NOT NULL AUTO_INCREMENT,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int,
PRIMARY KEY (Personid)
);
```
## Create Index
The `CREATE INDEX` statement is used to create indexes in tables.
The `CREATE INDEX` statement is used to create indexes in tables.
Indexes are used to retrieve data from the database more quickly than otherwise. The users cannot see the indexes, they are just used to speed up searches/queries.
@ -483,20 +483,20 @@ ON table_name (column1, column2, ...);
```
## Dates
**MySQL** comes with the following data types for storing a date or a date/time value in the database:
- `DATE` - format YYYY-MM-DD
- `DATETIME` - format: YYYY-MM-DD HH:MI:SS
- `TIMESTAMP` - format: YYYY-MM-DD HH:MI:SS
- `YEAR` - format YYYY or YY
**MySQL** comes with the following data types for storing a date or a date/time value in the database:
- `DATE` - format YYYY-MM-DD
- `DATETIME` - format: YYYY-MM-DD HH:MI:SS
- `TIMESTAMP` - format: YYYY-MM-DD HH:MI:SS
- `YEAR` - format YYYY or YY
## Data Types
### String
| Data type | Description |
| --------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| CHAR(size) | A FIXED length string (can contain letters, numbers, and special characters). The _size_ parameter specifies the column length in characters - can be from 0 to 255. Default is 1 |
| VARCHAR(size) | A VARIABLE length string (can contain letters, numbers, and special characters). The _size_ parameter specifies the maximum string length in characters - can be from 0 to 65535 |
| BINARY(size) | Equal to CHAR(), but stores binary byte strings. The _size_ parameter specifies the column length in bytes. Default is 1 |
| VARBINARY(size) | Equal to VARCHAR(), but stores binary byte strings. The _size_ parameter specifies the maximum column length in bytes. |
| CHAR(size) | A FIXED length string (can contain letters, numbers, and special characters). The _size_ parameter specifies the column length in characters - can be from 0 to 255. Default is 1 |
| VARCHAR(size) | A VARIABLE length string (can contain letters, numbers, and special characters). The _size_ parameter specifies the maximum string length in characters - can be from 0 to 65535 |
| BINARY(size) | Equal to CHAR(), but stores binary byte strings. The _size_ parameter specifies the column length in bytes. Default is 1 |
| VARBINARY(size) | Equal to VARCHAR(), but stores binary byte strings. The _size_ parameter specifies the maximum column length in bytes. |
| TINYBLOB | For BLOBs (Binary Large Objects). Max length: 255 bytes |
| TINYTEXT | Holds a string with a maximum length of 255 characters |
| TEXT(size) | Holds a string with a maximum length of 65,535 bytes |
@ -511,21 +511,21 @@ ON table_name (column1, column2, ...);
### Numeric
| Data type | Description |
| ----------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| BIT(_size_) | A bit-value type. The number of bits per value is specified in _size_. The _size_ parameter can hold a value from 1 to 64. The default value for _size_ is 1. |
| TINYINT(_size_) | A very small integer. Signed range is from -128 to 127. Unsigned range is from 0 to 255. The _size_ parameter specifies the maximum display width (which is 255) |
| BIT(_size_) | A bit-value type. The number of bits per value is specified in _size_. The _size_ parameter can hold a value from 1 to 64. The default value for _size_ is 1. |
| TINYINT(_size_) | A very small integer. Signed range is from -128 to 127. Unsigned range is from 0 to 255. The _size_ parameter specifies the maximum display width (which is 255) |
| BOOL | Zero is considered as false, nonzero values are considered as true. |
| BOOLEAN | Equal to BOOL |
| SMALLINT(_size_) | A small integer. Signed range is from -32768 to 32767. Unsigned range is from 0 to 65535. The _size_ parameter specifies the maximum display width (which is 255) |
| MEDIUMINT(_size_) | A medium integer. Signed range is from -8388608 to 8388607. Unsigned range is from 0 to 16777215. The _size_ parameter specifies the maximum display width (which is 255) |
| INT(_size_) | A medium integer. Signed range is from -2147483648 to 2147483647. Unsigned range is from 0 to 4294967295. The _size_ parameter specifies the maximum display width (which is 255) |
| SMALLINT(_size_) | A small integer. Signed range is from -32768 to 32767. Unsigned range is from 0 to 65535. The _size_ parameter specifies the maximum display width (which is 255) |
| MEDIUMINT(_size_) | A medium integer. Signed range is from -8388608 to 8388607. Unsigned range is from 0 to 16777215. The _size_ parameter specifies the maximum display width (which is 255) |
| INT(_size_) | A medium integer. Signed range is from -2147483648 to 2147483647. Unsigned range is from 0 to 4294967295. The _size_ parameter specifies the maximum display width (which is 255) |
| INTEGER(_size_) | Equal to INT(size) |
| BIGINT(_size_) | A large integer. Signed range is from -9223372036854775808 to 9223372036854775807. Unsigned range is from 0 to 18446744073709551615. The _size_ parameter specifies the maximum display width (which is 255) |
| FLOAT(_size_, _d_) | A floating point number. The total number of digits is specified in _size_. The number of digits after the decimal point is specified in the _d_ parameter. This syntax is deprecated in MySQL 8.0.17, and it will be removed in future MySQL versions |
| FLOAT(_p_) | A floating point number. MySQL uses the _p_ value to determine whether to use FLOAT or DOUBLE for the resulting data type. If _p_ is from 0 to 24, the data type becomes FLOAT(). If _p_ is from 25 to 53, the data type becomes DOUBLE() |
| DOUBLE(_size_, _d_) | A normal-size floating point number. The total number of digits is specified in _size_. The number of digits after the decimal point is specified in the _d_ parameter |
| DOUBLE PRECISION(_size_, _d_) | |
| DECIMAL(_size_, _d_) | An exact fixed-point number. The total number of digits is specified in _size_. The number of digits after the decimal point is specified in the _d_ parameter. The maximum number for _size_ is 65. The maximum number for _d_ is 30. The default value for _size_ is 10. The default value for _d_ is 0. |
| DEC(_size_, _d_) | Equal to DECIMAL(size,d) |
| BIGINT(_size_) | A large integer. Signed range is from -9223372036854775808 to 9223372036854775807. Unsigned range is from 0 to 18446744073709551615. The _size_ parameter specifies the maximum display width (which is 255) |
| FLOAT(_size_, _d_) | A floating point number. The total number of digits is specified in _size_. The number of digits after the decimal point is specified in the _d_ parameter. This syntax is deprecated in MySQL 8.0.17, and it will be removed in future MySQL versions |
| FLOAT(_p_) | A floating point number. MySQL uses the _p_ value to determine whether to use FLOAT or DOUBLE for the resulting data type. If _p_ is from 0 to 24, the data type becomes FLOAT(). If _p_ is from 25 to 53, the data type becomes DOUBLE() |
| DOUBLE(_size_, _d_) | A normal-size floating point number. The total number of digits is specified in _size_. The number of digits after the decimal point is specified in the _d_ parameter |
| DOUBLE PRECISION(_size_, _d_) | |
| DECIMAL(_size_, _d_) | An exact fixed-point number. The total number of digits is specified in _size_. The number of digits after the decimal point is specified in the _d_ parameter. The maximum number for _size_ is 65. The maximum number for _d_ is 30. The default value for _size_ is 10. The default value for _d_ is 0. |
| DEC(_size_, _d_) | Equal to DECIMAL(size,d) |
### Date & Time
| Data type | Description |
@ -570,7 +570,7 @@ SELECT UPPER("SQL");
The `TRIM()` function removes leading and trailing spaces from a string. `LTRIM()` & `RTRIM()` remove leading and trailing spaces from the left or right respectively.
```sql
SELECT TRIM('    SQL    ') AS TrimmedString;
SELECT TRIM(' SQL ') AS TrimmedString;
```
### SUBSTRING()
@ -602,7 +602,7 @@ The `REVERSE()` function reverses a string and returns the result.
The `REPLACE()` function replaces all occurrences of a substring within a string, with a new substring.
```sql
REPLACE(string, from_string, new_string)
REPLACE(string, from_string, new_string)
```
### REPEAT()
@ -614,50 +614,50 @@ REPEAT(string, number)
## Numeric Functions
### MIN() & MAX()
The `MIN()` function returns the smallest value of the selected column.
The `MIN()` function returns the smallest value of the selected column.
The `MAX()` function returns the largest value of the selected column.
The `MAX()` function returns the largest value of the selected column.
```sql
SELECT MIN(Price)
FROM Products;
SELECT MIN(Price)
FROM Products;
SELECT MAX(Price)
FROM Products;
SELECT MAX(Price)
FROM Products;
```
### COUNT()
The `COUNT()` function returns the number of rows that matches a specified criterion.
The `COUNT()` function returns the number of rows that matches a specified criterion.
```sql
SELECT COUNT(*)
FROM Products;
SELECT COUNT(*)
FROM Products;
```
### SUM()
The `SUM()` function returns the total sum of a numeric column.
The `SUM()` function returns the total sum of a numeric column.
Example:
```sql
SELECT SUM(Quantity) AS total
FROM OrderDetails;
SELECT SUM(Quantity) AS total
FROM OrderDetails;
```
Expressions:
```sql
SELECT SUM(Quantity * 10)
FROM OrderDetails;
SELECT SUM(Quantity * 10)
FROM OrderDetails;
```
### AVG()
The `AVG()` function returns the average value of a numeric column.
The `AVG()` function returns the average value of a numeric column.
```sql
SELECT AVG(Price)
FROM Products;
SELECT AVG(Price)
FROM Products;
SELECT * FROM Products
WHERE price > (SELECT AVG(price) FROM Products);
SELECT * FROM Products
WHERE price > (SELECT AVG(price) FROM Products);
```
## Date Functions