diff --git a/htdocs/install/mysql/tables/llx_commandedet.sql b/htdocs/install/mysql/tables/llx_commandedet.sql
index 93999b6f60e..0d6468309f5 100644
--- a/htdocs/install/mysql/tables/llx_commandedet.sql
+++ b/htdocs/install/mysql/tables/llx_commandedet.sql
@@ -45,7 +45,7 @@ create table llx_commandedet
   total_localtax1				double(24,8) DEFAULT 0,          -- Total LocalTax1 
   total_localtax2				double(24,8) DEFAULT 0,          -- Total LocalTax2
   total_ttc						double(24,8) DEFAULT 0,          -- Total TTC de la ligne toute quantite et incluant remise ligne et globale
-  product_type					integer      DEFAULT 0,
+  product_type					integer      DEFAULT 0,          -- 0 or 1. Value 9 may be used by some modules (amount of line may not be included into generated discount if value is 9).
   date_start					datetime     DEFAULT NULL,       -- date debut si service
   date_end						datetime     DEFAULT NULL,       -- date fin si service
   info_bits						integer      DEFAULT 0,          -- TVA NPR ou non
diff --git a/htdocs/install/mysql/tables/llx_facturedet.sql b/htdocs/install/mysql/tables/llx_facturedet.sql
index 77d87c68c23..05c68e92751 100644
--- a/htdocs/install/mysql/tables/llx_facturedet.sql
+++ b/htdocs/install/mysql/tables/llx_facturedet.sql
@@ -47,7 +47,7 @@ create table llx_facturedet
   total_localtax1				double(24,8) DEFAULT 0,				-- Total LocalTax1 for total quantity of line
   total_localtax2				double(24,8) DEFAULT 0,				-- Total LocalTax2 for total quantity of line
   total_ttc						double(24,8),						-- Total TTC de la ligne toute quantite et incluant remise ligne et globale
-  product_type					integer    DEFAULT 0,
+  product_type					integer    DEFAULT 0,				-- 0 or 1. Value 9 may be used by some modules (amount of line may not be included into generated discount if value is 9).
   date_start					datetime   DEFAULT NULL,			-- date start if service
   date_end						datetime   DEFAULT NULL,			-- date end if service
   info_bits						integer    DEFAULT 0,				-- VAT NPR or not (for france only)
diff --git a/htdocs/install/mysql/tables/llx_propaldet.sql b/htdocs/install/mysql/tables/llx_propaldet.sql
index 808e7b54ad3..283708fd7ce 100644
--- a/htdocs/install/mysql/tables/llx_propaldet.sql
+++ b/htdocs/install/mysql/tables/llx_propaldet.sql
@@ -44,7 +44,7 @@ create table llx_propaldet
   total_localtax1					double(24,8) DEFAULT 0,          -- Total localtax1
   total_localtax2					double(24,8) DEFAULT 0,          -- Total localtax2
   total_ttc							double(24,8) DEFAULT 0,          -- Total TTC de la ligne toute quantite et incluant remise ligne et globale
-  product_type						integer    DEFAULT 0,
+  product_type						integer    DEFAULT 0,            -- 0 or 1. Value 9 may be used by some modules (amount of line may not be included into generated discount if value is 9).
   date_start						datetime   DEFAULT NULL,         -- date debut si service
   date_end							datetime   DEFAULT NULL,         -- date fin si service
   info_bits							integer      DEFAULT 0,          -- TVA NPR ou non