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

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

CREATE TABLE Users(
Id INT PRIMARY KEY IDENTITY,
Nickname VARCHAR(25),
Gender CHAR(1),
Age INT,
LocationId INT,
CredentialId INT UNIQUE,
CONSTRAINT fk_Users_Locations FOREIGN KEY (LocationId)
REFERENCES Locations(Id),
CONSTRAINT fk_Users_Credentials FOREIGN KEY (CredentialId)
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 (UserId, ChatId),
CONSTRAINT fk_UsersChats_Users FOREIGN KEY (UserId)
REFERENCES Users(Id),
CONSTRAINT fk_UsersChats_Chats FOREIGN KEY (ChatId)
REFERENCES Chats(Id)
)