diff --git a/freqtrade/persistence/models.py b/freqtrade/persistence/models.py
index 428455ff8..f2e7a10c4 100644
--- a/freqtrade/persistence/models.py
+++ b/freqtrade/persistence/models.py
@@ -112,15 +112,15 @@ class Order(_DECL_BASE):
 
     trade = relationship("Trade", back_populates="orders")
 
-    ft_order_side = Column(String, nullable=False)
-    ft_pair = Column(String, nullable=False)
+    ft_order_side = Column(String(25), nullable=False)
+    ft_pair = Column(String(25), nullable=False)
     ft_is_open = Column(Boolean, nullable=False, default=True, index=True)
 
-    order_id = Column(String, nullable=False, index=True)
-    status = Column(String, nullable=True)
-    symbol = Column(String, nullable=True)
-    order_type = Column(String, nullable=True)
-    side = Column(String, nullable=True)
+    order_id = Column(String(255), nullable=False, index=True)
+    status = Column(String(255), nullable=True)
+    symbol = Column(String(25), nullable=True)
+    order_type = Column(String(50), nullable=True)
+    side = Column(String(25), nullable=True)
     price = Column(Float, nullable=True)
     average = Column(Float, nullable=True)
     amount = Column(Float, nullable=True)
@@ -658,15 +658,15 @@ class Trade(_DECL_BASE, LocalTrade):
 
     orders = relationship("Order", order_by="Order.id", cascade="all, delete-orphan")
 
-    exchange = Column(String, nullable=False)
-    pair = Column(String, nullable=False, index=True)
+    exchange = Column(String(25), nullable=False)
+    pair = Column(String(25), nullable=False, index=True)
     is_open = Column(Boolean, nullable=False, default=True, index=True)
     fee_open = Column(Float, nullable=False, default=0.0)
     fee_open_cost = Column(Float, nullable=True)
-    fee_open_currency = Column(String, nullable=True)
+    fee_open_currency = Column(String(25), nullable=True)
     fee_close = Column(Float, nullable=False, default=0.0)
     fee_close_cost = Column(Float, nullable=True)
-    fee_close_currency = Column(String, nullable=True)
+    fee_close_currency = Column(String(25), nullable=True)
     open_rate = Column(Float)
     open_rate_requested = Column(Float)
     # open_trade_value - calculated via _calc_open_trade_value
@@ -680,7 +680,7 @@ class Trade(_DECL_BASE, LocalTrade):
     amount_requested = Column(Float)
     open_date = Column(DateTime, nullable=False, default=datetime.utcnow)
     close_date = Column(DateTime)
-    open_order_id = Column(String)
+    open_order_id = Column(String(255))
     # absolute value of the stop loss
     stop_loss = Column(Float, nullable=True, default=0.0)
     # percentage value of the stop loss
@@ -690,16 +690,16 @@ class Trade(_DECL_BASE, LocalTrade):
     # percentage value of the initial stop loss
     initial_stop_loss_pct = Column(Float, nullable=True)
     # stoploss order id which is on exchange
-    stoploss_order_id = Column(String, nullable=True, index=True)
+    stoploss_order_id = Column(String(255), nullable=True, index=True)
     # last update time of the stoploss order on exchange
     stoploss_last_update = Column(DateTime, nullable=True)
     # absolute value of the highest reached price
     max_rate = Column(Float, nullable=True, default=0.0)
     # Lowest price reached
     min_rate = Column(Float, nullable=True)
-    sell_reason = Column(String, nullable=True)
-    sell_order_status = Column(String, nullable=True)
-    strategy = Column(String, nullable=True)
+    sell_reason = Column(String(100), nullable=True)
+    sell_order_status = Column(String(100), nullable=True)
+    strategy = Column(String(100), nullable=True)
     timeframe = Column(Integer, nullable=True)
 
     def __init__(self, **kwargs):
@@ -856,8 +856,8 @@ class PairLock(_DECL_BASE):
 
     id = Column(Integer, primary_key=True)
 
-    pair = Column(String, nullable=False, index=True)
-    reason = Column(String, nullable=True)
+    pair = Column(String(25), nullable=False, index=True)
+    reason = Column(String(255), nullable=True)
     # Time the pair was locked (start time)
     lock_time = Column(DateTime, nullable=False)
     # Time until the pair is locked (end time)