CREATE TABLE Locations
(
Id INT PRIMARY KEY,
Latitude FLOAT,
Longitude FLOAT
)

CREATE TABLE Credentials
(
Id INT PRIMARY KEY,
Email VARCHAR(30),
Password VARCHAR(20)
)

CREATE TABLE Users
(
Id INT IDENTITY PRIMARY KEY,
Nickname VARCHAR(25),
Gender CHAR(1),
Age INT,
Location_id INT,
Credential_id INT UNIQUE,
CONSTRAINT FK_Users_Locations FOREIGN KEY (Location_id) REFERENCES Locations (Id),
CONSTRAINT FK_Users_Credentials FOREIGN KEY (Credential_id) REFERENCES Credentials (Id)
)

CREATE TABLE Chats
(
Id INT PRIMARY KEY,
Title VARCHAR(32),
StartDate DATE,
IsActive Bit
)

CREATE TABLE Messages
(
Id INT PRIMARY KEY,
Content VARCHAR(200),
SentOn DATE,
ChatId INT,
UserId INT,
CONSTRAINT FK_Messages_Chats FOREIGN KEY (ChatId) REFERENCES Chats (Id),
CONSTRAINT FK_Messages_Users FOREIGN KEY (UserId) REFERENCES Users (Id)
)

CREATE TABLE UsersChats
(
UserId INT,
ChatId INT,
CONSTRAINT PK_UsersChats PRIMARY KEY (ChatId, UserId),
CONSTRAINT FK_UsersChats_Users FOREIGN KEY (UserId) REFERENCES Users (Id),
CONSTRAINT FK_UsersChats_Chats FOREIGN KEY (ChatId) REFERENCES Chats (Id)
)