diff --git a/args/schema.sql b/args/schema.sql
index e9e9376..c970b8b 100644
--- a/args/schema.sql
+++ b/args/schema.sql
@@ -12,21 +12,24 @@ floID CHAR(34) NOT NULL,
 proxyKey CHAR(66) NOT NULL,
 session_id VARCHAR(100) UNIQUE,
 session_time DATETIME DEFAULT CURRENT_TIMESTAMP,
-PRIMARY KEY(floID)
+PRIMARY KEY(floID),
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE Request_Log(
 floID CHAR(34) NOT NULL,
 request TEXT NOT NULL,
 sign TEXT NOT NULL,
-request_time DATETIME DEFAULT CURRENT_TIMESTAMP
+request_time DATETIME DEFAULT CURRENT_TIMESTAMP,
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE Cash (
 id INT NOT NULL AUTO_INCREMENT,
 floID CHAR(34) NOT NULL UNIQUE,
 rupeeBalance DECIMAL(12, 2) DEFAULT 0.00,
-PRIMARY KEY(id)
+PRIMARY KEY(id),
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE Vault (
@@ -35,7 +38,8 @@ floID CHAR(34) NOT NULL,
 locktime DATETIME DEFAULT CURRENT_TIMESTAMP,
 base DECIMAL(10, 2),
 quantity FLOAT NOT NULL,
-PRIMARY KEY(id)
+PRIMARY KEY(id),
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE SellOrder (
@@ -44,7 +48,8 @@ floID CHAR(34) NOT NULL,
 quantity FLOAT NOT NULL,
 minPrice DECIMAL(10, 2),
 time_placed DATETIME DEFAULT CURRENT_TIMESTAMP,
-PRIMARY KEY(id)
+PRIMARY KEY(id),
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE BuyOrder (
@@ -53,7 +58,8 @@ floID CHAR(34) NOT NULL,
 quantity FLOAT NOT NULL,
 maxPrice DECIMAL(10, 2) NOT NULL,
 time_placed DATETIME DEFAULT CURRENT_TIMESTAMP,
-PRIMARY KEY(id)
+PRIMARY KEY(id),
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE Transactions (
@@ -61,7 +67,9 @@ seller CHAR(34) NOT NULL,
 buyer CHAR(34) NOT NULL,
 quantity FLOAT NOT NULL,
 unitValue DECIMAL(10, 2) NOT NULL,
-tx_time DATETIME DEFAULT CURRENT_TIMESTAMP
+tx_time DATETIME DEFAULT CURRENT_TIMESTAMP,
+FOREIGN KEY (buyer) REFERENCES Users(floID),
+FOREIGN KEY (seller) REFERENCES Users(floID)
 );
 
 CREATE TABLE inputFLO (
@@ -70,7 +78,8 @@ txid VARCHAR(128) NOT NULL,
 floID CHAR(34) NOT NULL,
 amount FLOAT,
 status VARCHAR(50) NOT NULL,
-PRIMARY KEY(id)
+PRIMARY KEY(id),
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE outputFLO (
@@ -79,7 +88,8 @@ txid VARCHAR(128),
 floID CHAR(34) NOT NULL,
 amount FLOAT NOT NULL,
 status VARCHAR(50) NOT NULL,
-PRIMARY KEY(id)
+PRIMARY KEY(id),
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE inputRupee (
@@ -88,7 +98,8 @@ txid VARCHAR(128) NOT NULL,
 floID CHAR(34) NOT NULL,
 amount FLOAT,
 status VARCHAR(50) NOT NULL,
-PRIMARY KEY(id)
+PRIMARY KEY(id),
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE outputRupee (
@@ -97,7 +108,8 @@ txid VARCHAR(128),
 floID CHAR(34) NOT NULL,
 amount FLOAT NOT NULL,
 status VARCHAR(50) NOT NULL,
-PRIMARY KEY(id)
+PRIMARY KEY(id),
+FOREIGN KEY (floID) REFERENCES Users(floID)
 );
 
 CREATE TABLE TagList (
@@ -115,7 +127,9 @@ id INT NOT NULL AUTO_INCREMENT,
 floID CHAR(34) NOT NULL,
 tag VARCHAR(50) NOT NULL,
 PRIMARY KEY(floID, tag),
-KEY (id)
+KEY (id),
+FOREIGN KEY (floID) REFERENCES Users(floID),
+FOREIGN KEY (tag) REFERENCES TagList(tag)
 );
 
 CREATE TABLE priceHistory (
diff --git a/src/group.js b/src/group.js
index 84c3dbb..03d402b 100644
--- a/src/group.js
+++ b/src/group.js
@@ -9,6 +9,8 @@ function addTag(floID, tag) {
             .catch(error => {
                 if (error.code === "ER_DUP_ENTRY")
                     reject(INVALID(`${floID} already in ${tag}`));
+                else if (error.code === "ER_NO_REFERENCED_ROW")
+                    reject(INVALID(`Invalid user-floID and/or Tag`));
                 else
                     reject(error);
             });