diff --git a/Impala/OMOP_CDM_ddl_Impala.sql b/Impala/OMOP_CDM_ddl_Impala.sql
index d1ade63..5901e8e 100644
--- a/Impala/OMOP_CDM_ddl_Impala.sql
+++ b/Impala/OMOP_CDM_ddl_Impala.sql
@@ -50,11 +50,11 @@ CREATE TABLE concept (
  domain_id VARCHAR(20),
  vocabulary_id VARCHAR(20),
  concept_class_id VARCHAR(20),
- standard_concept VARCHAR(1),
+ standard_concept CHAR(1),
  concept_code VARCHAR(50),
  valid_start_date VARCHAR(8), -- DATE
  valid_end_date VARCHAR(8), -- DATE
- invalid_reason VARCHAR(1)
+ invalid_reason CHAR(1)
 )
 ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t'
 TBLPROPERTIES ("skip.header.line.count"="1")
@@ -106,7 +106,7 @@ CREATE TABLE concept_relationship (
  relationship_id VARCHAR(20),
  valid_start_date VARCHAR(8), -- DATE
  valid_end_date VARCHAR(8), -- DATE
- invalid_reason VARCHAR(1)
+ invalid_reason CHAR(1)
 )
 ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t'
 TBLPROPERTIES ("skip.header.line.count"="1")
@@ -117,8 +117,8 @@ TBLPROPERTIES ("skip.header.line.count"="1")
 CREATE TABLE relationship (
  relationship_id VARCHAR(20),
  relationship_name VARCHAR(255),
- is_hierarchical VARCHAR(1),
- defines_ancestry VARCHAR(1),
+ is_hierarchical CHAR(1),
+ defines_ancestry CHAR(1),
  reverse_relationship_id VARCHAR(20),
  relationship_concept_id INTEGER
 )
@@ -158,7 +158,7 @@ CREATE TABLE source_to_concept_map (
  target_vocabulary_id VARCHAR(20),
  valid_start_date VARCHAR(8), -- DATE
  valid_end_date VARCHAR(8), -- DATE
- invalid_reason VARCHAR(1)
+ invalid_reason CHAR(1)
 )
 ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t'
 TBLPROPERTIES ("skip.header.line.count"="1")
@@ -179,7 +179,7 @@ CREATE TABLE drug_strength (
  box_size INTEGER,
  valid_start_date VARCHAR(8), -- DATE
  valid_end_date VARCHAR(8), -- DATE
- invalid_reason VARCHAR(1)
+ invalid_reason CHAR(1)
 )
 ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t'
 TBLPROPERTIES ("skip.header.line.count"="1")
@@ -486,7 +486,7 @@ CREATE TABLE note_nlp (
  nlp_system VARCHAR(250),
  nlp_date VARCHAR(8),
  nlp_datetime VARCHAR(10),
- term_exists VARCHAR(1),
+ term_exists CHAR(1),
  term_temporal VARCHAR(50),
  term_modifiers VARCHAR(2000)
  )
@@ -543,7 +543,7 @@ CREATE TABLE `location` (
  address_1 VARCHAR(50),
  address_2 VARCHAR(50),
  city VARCHAR(50),
- state VARCHAR(2),
+ state CHAR(2),
  zip VARCHAR(9),
  county VARCHAR(20),
  location_source_value VARCHAR(50)
@@ -631,7 +631,7 @@ CREATE TABLE cost (
  revenue_code_concept_id INTEGER,
  reveue_code_source_value VARCHAR(50),
  drg_concept_id			INTEGER,
- drg_source_value		VARCHAR(3)
+ drg_source_value		CHAR(3)
 )
 ;
 
diff --git a/Oracle/OMOP CDM ddl - Oracle.sql b/Oracle/OMOP CDM ddl - Oracle.sql
index 76011cc..124812c 100644
--- a/Oracle/OMOP CDM ddl - Oracle.sql	
+++ b/Oracle/OMOP CDM ddl - Oracle.sql	
@@ -49,11 +49,11 @@ CREATE TABLE concept (
   domain_id				VARCHAR(20)		NOT NULL,
   vocabulary_id			VARCHAR(20)		NOT NULL,
   concept_class_id		VARCHAR(20)		NOT NULL,
-  standard_concept		VARCHAR(1)		NULL,
+  standard_concept		CHAR(1)		NULL,
   concept_code			VARCHAR(50)		NOT NULL,
   valid_start_date		DATE			NOT NULL,
   valid_end_date		DATE			NOT NULL,
-  invalid_reason		VARCHAR(1)		NULL
+  invalid_reason		CHAR(1)		NULL
 )
 ;
 
@@ -97,7 +97,7 @@ CREATE TABLE concept_relationship (
   relationship_id		VARCHAR(20)		NOT NULL,
   valid_start_date		DATE			NOT NULL,
   valid_end_date		DATE			NOT NULL,
-  invalid_reason		VARCHAR(1)		NULL)
+  invalid_reason		CHAR(1)		NULL)
 ;
 
 
@@ -105,8 +105,8 @@ CREATE TABLE concept_relationship (
 CREATE TABLE relationship (
   relationship_id			VARCHAR(20)		NOT NULL,
   relationship_name			VARCHAR(255)	NOT NULL,
-  is_hierarchical			VARCHAR(1)		NOT NULL,
-  defines_ancestry			VARCHAR(1)		NOT NULL,
+  is_hierarchical			CHAR(1)		NOT NULL,
+  defines_ancestry			CHAR(1)		NOT NULL,
   reverse_relationship_id	VARCHAR(20)		NOT NULL,
   relationship_concept_id	INTEGER			NOT NULL
 )
@@ -140,7 +140,7 @@ CREATE TABLE source_to_concept_map (
   target_vocabulary_id		VARCHAR(20)		NOT NULL,
   valid_start_date			DATE			NOT NULL,
   valid_end_date			DATE			NOT NULL,
-  invalid_reason			VARCHAR(1)		NULL
+  invalid_reason			CHAR(1)		NULL
 )
 ;
 
@@ -159,7 +159,7 @@ CREATE TABLE drug_strength (
   box_size						INTEGER		NULL,
   valid_start_date				DATE		NOT NULL,
   valid_end_date				DATE		NOT NULL,
-  invalid_reason				VARCHAR(1)	NULL
+  invalid_reason				CHAR(1)	NULL
 )
 ;
 
@@ -471,7 +471,7 @@ CREATE TABLE note_nlp
   nlp_system					VARCHAR(250)	NULL ,
   nlp_date						DATE			NOT NULL ,
   nlp_datetime					TIMESTAMP WITH TIME ZONE		NULL ,
-  term_exists					VARCHAR(1)		NULL ,
+  term_exists					CHAR(1)		NULL ,
   term_temporal					VARCHAR(50)		NULL ,
   term_modifiers				VARCHAR(2000)	NULL
 )
@@ -528,7 +528,7 @@ CREATE TABLE location
      address_1						VARCHAR(50)		NULL , 
      address_2						VARCHAR(50)		NULL , 
      city							VARCHAR(50)		NULL , 
-     state							VARCHAR(2)		NULL , 
+     state							CHAR(2)		NULL , 
      zip							VARCHAR(9)		NULL , 
      county							VARCHAR(20)		NULL , 
      location_source_value			VARCHAR(50)		NULL
@@ -615,7 +615,7 @@ CREATE TABLE cost
      revenue_code_concept_id		INTEGER			NULL , 
      reveue_code_source_value    VARCHAR2(50)   NULL ,
 	 drg_concept_id			INTEGER		NULL,
-     drg_source_value		VARCHAR(3)		NULL
+     drg_source_value		CHAR(3)		NULL
     ) 
 ;
 
diff --git a/PostgreSQL/OMOP CDM ddl - PostgreSQL.sql b/PostgreSQL/OMOP CDM ddl - PostgreSQL.sql
index acc06c6..eea33f0 100644
--- a/PostgreSQL/OMOP CDM ddl - PostgreSQL.sql	
+++ b/PostgreSQL/OMOP CDM ddl - PostgreSQL.sql	
@@ -49,11 +49,11 @@ CREATE TABLE concept (
   domain_id				VARCHAR(20)		NOT NULL,
   vocabulary_id			VARCHAR(20)		NOT NULL,
   concept_class_id		VARCHAR(20)		NOT NULL,
-  standard_concept		VARCHAR(1)		NULL,
+  standard_concept		CHAR(1)		NULL,
   concept_code			VARCHAR(50)		NOT NULL,
   valid_start_date		DATE			NOT NULL,
   valid_end_date		DATE			NOT NULL,
-  invalid_reason		VARCHAR(1)		NULL
+  invalid_reason		CHAR(1)		NULL
 )
 ;
 
@@ -97,7 +97,7 @@ CREATE TABLE concept_relationship (
   relationship_id		VARCHAR(20)		NOT NULL,
   valid_start_date		DATE			NOT NULL,
   valid_end_date		DATE			NOT NULL,
-  invalid_reason		VARCHAR(1)		NULL)
+  invalid_reason		CHAR(1)		NULL)
 ;
 
 
@@ -105,8 +105,8 @@ CREATE TABLE concept_relationship (
 CREATE TABLE relationship (
   relationship_id			VARCHAR(20)		NOT NULL,
   relationship_name			VARCHAR(255)	NOT NULL,
-  is_hierarchical			VARCHAR(1)		NOT NULL,
-  defines_ancestry			VARCHAR(1)		NOT NULL,
+  is_hierarchical			CHAR(1)		NOT NULL,
+  defines_ancestry			CHAR(1)		NOT NULL,
   reverse_relationship_id	VARCHAR(20)		NOT NULL,
   relationship_concept_id	INTEGER			NOT NULL
 )
@@ -140,7 +140,7 @@ CREATE TABLE source_to_concept_map (
   target_vocabulary_id		VARCHAR(20)		NOT NULL,
   valid_start_date			DATE			NOT NULL,
   valid_end_date			DATE			NOT NULL,
-  invalid_reason			VARCHAR(1)		NULL
+  invalid_reason			CHAR(1)		NULL
 )
 ;
 
@@ -159,7 +159,7 @@ CREATE TABLE drug_strength (
   box_size						INTEGER		NULL,
   valid_start_date				DATE		NOT NULL,
   valid_end_date				DATE		NOT NULL,
-  invalid_reason				VARCHAR(1)	NULL
+  invalid_reason				CHAR(1)	NULL
 )
 ;
 
@@ -472,7 +472,7 @@ CREATE TABLE note_nlp
   nlp_system					VARCHAR(250)	NULL ,
   nlp_date						DATE			NOT NULL ,
   nlp_datetime					TIMESTAMP		NULL ,
-  term_exists					VARCHAR(1)		NULL ,
+  term_exists					CHAR(1)		NULL ,
   term_temporal					VARCHAR(50)		NULL ,
   term_modifiers				VARCHAR(2000)	NULL
 )
@@ -530,7 +530,7 @@ CREATE TABLE location
      address_1						VARCHAR(50)		NULL , 
      address_2						VARCHAR(50)		NULL , 
      city							VARCHAR(50)		NULL , 
-     state							VARCHAR(2)		NULL , 
+     state							CHAR(2)		NULL , 
      zip							VARCHAR(9)		NULL , 
      county							VARCHAR(20)		NULL , 
      location_source_value			VARCHAR(50)		NULL
@@ -618,7 +618,7 @@ CREATE TABLE cost
      revenue_code_concept_id		INTEGER			NULL , 
      reveue_code_source_value    VARCHAR(50)   NULL ,
 	 drg_concept_id			INTEGER		NULL,
-     drg_source_value		VARCHAR(3)		NULL
+     drg_source_value		CHAR(3)		NULL
     ) 
 ;
 
diff --git a/Redshift/OMOP CDM ddl - Redshift.sql b/Redshift/OMOP CDM ddl - Redshift.sql
index 7af70af..8b79ce3 100644
--- a/Redshift/OMOP CDM ddl - Redshift.sql	
+++ b/Redshift/OMOP CDM ddl - Redshift.sql	
@@ -54,7 +54,7 @@ create table concept
     concept_code 		varchar(50)		null, 
     valid_start_date 	date			not null, 
     valid_end_date 		date			not null, 
-    invalid_reason 		varchar(1)		null
+    invalid_reason 		char(1)		null
 )
 diststyle all;
 
@@ -92,7 +92,7 @@ create table concept_relationship
     relationship_id		varchar(20) not null, 
     valid_start_date	date 		not null, 
     valid_end_date 		date 		not null, 
-    invalid_reason 		varchar(1) 	null
+    invalid_reason 		char(1) 	null
 )
 diststyle all;
 
@@ -101,8 +101,8 @@ create table relationship
 (
   relationship_id			varchar(20)		not null,
   relationship_name			varchar(255)	not null,
-  is_hierarchical			varchar(1)		not null,
-  defines_ancestry			varchar(1)		not null,
+  is_hierarchical			char(1)		not null,
+  defines_ancestry			char(1)		not null,
   reverse_relationship_id	varchar(20)		not null,
   relationship_concept_id	integer			not null
 )
@@ -137,7 +137,7 @@ create table source_to_concept_map
   target_vocabulary_id		varchar(20)		not null,
   valid_start_date			date			not null,
   valid_end_date			date			not null,
-  invalid_reason			varchar(1)		null
+  invalid_reason			char(1)		null
 )
 diststyle all;
 
@@ -154,7 +154,7 @@ create table drug_strength
   box_size						integer		null,
   valid_start_date				date		not null,
   valid_end_date				date		not null,
-  invalid_reason				varchar(1)	null
+  invalid_reason				char(1)	null
 )
 diststyle all;
 
@@ -474,7 +474,7 @@ CREATE TABLE note_nlp
   nlp_system					varchar(250)	null ,
   nlp_date						date			not null ,
   nlp_datetime					timestamp		null ,
-  term_exists					varchar(1)		null ,
+  term_exists					char(1)		null ,
   term_temporal					varchar(50)		null ,
   term_modifiers				varchar(2000)	null
 )
@@ -534,7 +534,7 @@ create table location
   address_1						varchar(50)		null ,
   address_2						varchar(50)		null ,
   city							varchar(50)		null ,
-  state							varchar(2)		null ,
+  state							char(2)		null ,
   zip							varchar(9)		null ,
   county						varchar(20)		null ,
   location_source_value			varchar(50)		null
@@ -705,7 +705,7 @@ create table cost
   revenue_code_concept_id	integer			null ,
   reveue_code_source_value  varchar(50)		null ,
   drg_concept_id			integer			null,
-  drg_source_value			varchar(3)		null
+  drg_source_value			char(3)		null
 )
 distkey(payer_plan_period_id)
 sortkey(payer_plan_period_id);
diff --git a/Sql Server/OMOP CDM ddl - SQL Server.sql b/Sql Server/OMOP CDM ddl - SQL Server.sql
index 87f20ba..6619fc0 100644
--- a/Sql Server/OMOP CDM ddl - SQL Server.sql	
+++ b/Sql Server/OMOP CDM ddl - SQL Server.sql	
@@ -529,7 +529,7 @@ CREATE TABLE location
   address_1						VARCHAR(50)		NULL ,
   address_2						VARCHAR(50)		NULL ,
   city							VARCHAR(50)		NULL ,
-  state							VARCHAR(2)		NULL ,
+  state							CHAR(2)		NULL ,
   zip							VARCHAR(9)		NULL ,
   county							VARCHAR(20)		NULL ,
   location_source_value			VARCHAR(50)		NULL
@@ -615,7 +615,7 @@ CREATE TABLE cost
   revenue_code_concept_id		INTEGER			NULL ,
   reveue_code_source_value    VARCHAR(50)    NULL,
   drg_concept_id			INTEGER		NULL,
-  drg_source_value			VARCHAR(3)		NULL
+  drg_source_value			CHAR(3)		NULL
 )
 ;