You will have to add a check for each character column into the Select Where statement.
Names Default To Here( 1 );
dt = New Table( "blood pressure",
	Add Rows( 20 ),
	New Column( "Subject",
		Numeric,
		"Continuous",
		Format( "Best", 10 ),
		Set Values( [1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5] )
	),
	New Column( "S_Dose_Col",
		Character,
		"Nominal",
		Set Values(
			{"A", "A", "A", "A", "A", "B", "B", "B", "B", "B", "Control", "Control",
			"Control", "Control", "Control", "Placebo", "Placebo", "Placebo",
			"Placebo", "Placebo"}
		)
	),
	New Column( "S_BP_8M_Col",
		Numeric,
		"Continuous",
		Format( "Best", 16 ),
		Set Values(
			[182.595915155309, 172.512940709438, 180.774421425438, 180.620679187184,
			., 171.439595422176, 174.589230394192, 179.109260746268,
			177.787439187438, ., 181.804016028632, ., 186.313144806757,
			175.347853139956, 181.103289178403, 181.288352739913, 178.777832744608,
			176.763152449944, 175.768608854708, 184.167672392284]
		)
	),
	New Column( "S_BP_12M_Col",
		Numeric,
		"Continuous",
		Format( "Fixed Dec", 5, 0 ),
		Set Values(
			[173.550216520736, 180.718560564297, 188.500473854652, 176.718084823659,
			., 181.462075626649, 180.330100756984, 172.886222586229,
			192.050244302843, ., 185.501158177984, 183.877324525276,
			179.931613365546, 180.493132509235, 174.944992509985, 177.663853371957,
			174.717037207769, 186.677919707096, 178.12326354079, 171.230704316198]
		)
	),
	New Column( "BP 6M",
		Numeric,
		"Continuous",
		Format( "Best", 16 ),
		Set Values(
			[180.116643270986, 180.917546679043, 177.384986937421, 182.381646560932,
			., 179.517397097984, ., 182.904992672503, 176.785646502378, .,
			178.209310795898, 186.575178728884, ., 177.2578428812, 180.642613381863,
			178.850703910826, 188.986597488081, 172.45356859494, 182.404679249467,
			182.335148506991]
		)
	),
	New Column( "BP 8W",
		Character,
		"Nominal",
		Set Values(
			{"173.797442210887", "170.201828509985", "188.441549950731",
			"176.337805749776", "Q", "183.021068043181", "183.498290114926",
			"187.881911714776", "184.924564594592", "", "177.186342937671", "",
			"171.059060559811", "184.517143208058", "179.143677395064",
			"178.211632365764", "190.546847185169", "179.666182707754",
			"176.614597739946", "181.334797218108"}
		)
	),
	New Column( "BP 12W",
		Numeric,
		"Continuous",
		Format( "Best", 16 ),
		Set Values(
			[178.416197148117, 178.839136233913, 175.346240386252, 172.773758285362,
			., 175.683661608275, 179.622232533597, 192.773275959188,
			172.499108408691, ., 176.573252982367, 174.72327532089, 172.873089144473,
			171.169474537616, 185.445956950321, 181.685844613992, 178.055520662495,
			182.726891244295, 178.320419876662, 186.395858538357]
		)
	),
	New Column( "BP 6W",
		Numeric,
		"Continuous",
		Format( "Best", 16 ),
		Set Values(
			[181.152265967985, 176.084997418848, 181.924943930192, 183.608276048664,
			., 174.15485890414, 172.866924129507, 169.793497264777, 179.464417655732,
			., 177.20643071091, 176.115218469266, 181.319863949352, .,
			183.622763290159, 178.639264502305, 176.991735583422, 177.924284755616,
			177.143465976767, 183.421182544757]
		)
	),
	New Column( "BP 8F",
		Numeric,
		"Continuous",
		Format( "Best", 16 ),
		Set Values(
			[171.278300921568, 175.161843431476, 183.12980493925, 183.04930217403, .,
			184.878981656321, 184.16481869131, 179.098192996471, 186.765084181627, .,
			182.640175499696, 179.80577644674, 179.038752187802, 175.727537977595,
			183.636564430071, 188.483289884327, 182.282596238225, 183.200306257339,
			175.856743742269, 183.517577768589]
		)
	),
	New Column( "BP 12F",
		Numeric,
		"Continuous",
		Format( "Best", 16 ),
		Set Values(
			[177.570953487335, 184.884491085702, 182.794049100295, 187.31279033708,
			., 182.387718653956, 184.653326274105, 184.653672194875,
			184.384583007231, ., 190.972901519754, 181.46178488602, 181.459302956398,
			184.604441269869, 173.249587056935, 183.125809166649, 187.951725739917,
			190.139279669601, 183.549834391574, 171.907000056173]
		)
	),
	New Column( "BP 6F",
		Numeric,
		"Continuous",
		Format( "Best", 16 ),
		Set Values(
			[170.514896659448, 187.603078247176, 180.121927541929, 182.931206367403,
			., 184.169322994033, 180.368840760416, 170.403578559484,
			177.427685029706, ., 174.986928330607, 184.070139882305,
			189.242086812316, 169.540004898628, 185.21824057543, 173.182049720424,
			170.940897197153, 177.823031925273, 183.621024712236, 178.774574166082]
		)
	)
);
Names Default To Here( 1 );
dt = New Table( "blood pressure",
	Add Rows( 20 ),
	New Column( "Subject", Set Values( [1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5] ) ),
	New Column( "S_Dose_Col",
		character,
		"Nominal",
		Set Values(
			{"A", "A", "A", "A", "A", "B", "B", "B", "B", "B", "Control", "Control", "Control", "Control",
			"Control", "Placebo", "Placebo", "Placebo", "Placebo", "Placebo"}
		)
	),
	New Column( "S_BP_8M_Col",
		Numeric,
		Set Values(
			[182.595915155309, 172.512940709438, 180.774421425438, 180.620679187184, ., 171.439595422176,
			174.589230394192, 179.109260746268, 177.787439187438, ., 181.804016028632, ., 186.313144806757,
			175.347853139956, 181.103289178403, 181.288352739913, 178.777832744608, 176.763152449944,
			175.768608854708, 184.167672392284]
		)
	),
	New Column( "S_BP_12M_Col",
		Numeric,
		"Continuous",
		Format( "Fixed Dec", 5, 0 ),
		Set Values(
			[173.550216520736, 180.718560564297, 188.500473854652, 176.718084823659, ., 181.462075626649,
			180.330100756984, 172.886222586229, 192.050244302843, ., 185.501158177984, 183.877324525276,
			179.931613365546, 180.493132509235, 174.944992509985, 177.663853371957, 174.717037207769,
			186.677919707096, 178.12326354079, 171.230704316198]
		)
	),
	New Column( "BP 6M",
		Numeric,
		Set Values(
			[180.116643270986, 180.917546679043, 177.384986937421, 182.381646560932, ., 179.517397097984, .,
			182.904992672503, 176.785646502378, ., 178.209310795898, 186.575178728884, ., 177.2578428812,
			180.642613381863, 178.850703910826, 188.986597488081, 172.45356859494, 182.404679249467,
			182.335148506991]
		)
	),
	New Column( "BP 8W",
		Numeric,
		Set Values(
			[173.797442210887, 170.201828509985, 188.441549950731, 176.337805749776, ., 183.021068043181,
			183.498290114926, 187.881911714776, 184.924564594592, ., 177.186342937671, ., 171.059060559811,
			184.517143208058, 179.143677395064, 178.211632365764, 190.546847185169, 179.666182707754,
			176.614597739946, 181.334797218108]
		)
	),
	New Column( "BP 12W",
		Numeric,
		Set Values(
			[178.416197148117, 178.839136233913, 175.346240386252, 172.773758285362, ., 175.683661608275,
			179.622232533597, 192.773275959188, 172.499108408691, ., 176.573252982367, 174.72327532089,
			172.873089144473, 171.169474537616, 185.445956950321, 181.685844613992, 178.055520662495,
			182.726891244295, 178.320419876662, 186.395858538357]
		)
	),
	New Column( "BP 6W",
		Numeric,
		Set Values(
			[181.152265967985, 176.084997418848, 181.924943930192, 183.608276048664, ., 174.15485890414,
			172.866924129507, 169.793497264777, 179.464417655732, ., 177.20643071091, 176.115218469266,
			181.319863949352, ., 183.622763290159, 178.639264502305, 176.991735583422, 177.924284755616,
			177.143465976767, 183.421182544757]
		)
	),
	New Column( "BP 8F",
		Numeric,
		Set Values(
			[171.278300921568, 175.161843431476, 183.12980493925, 183.04930217403, ., 184.878981656321,
			184.16481869131, 179.098192996471, 186.765084181627, ., 182.640175499696, 179.80577644674,
			179.038752187802, 175.727537977595, 183.636564430071, 188.483289884327, 182.282596238225,
			183.200306257339, 175.856743742269, 183.517577768589]
		)
	),
	New Column( "BP 12F",
		Numeric,
		Set Values(
			[177.570953487335, 184.884491085702, 182.794049100295, 187.31279033708, ., 182.387718653956,
			184.653326274105, 184.653672194875, 184.384583007231, ., 190.972901519754, 181.46178488602,
			181.459302956398, 184.604441269869, 173.249587056935, 183.125809166649, 187.951725739917,
			190.139279669601, 183.549834391574, 171.907000056173]
		)
	),
	New Column( "BP 6F",
		Numeric,
		Set Values(
			[170.514896659448, 187.603078247176, 180.121927541929, 182.931206367403, ., 184.169322994033,
			180.368840760416, 170.403578559484, 177.427685029706, ., 174.986928330607, 184.070139882305,
			189.242086812316, 169.540004898628, 185.21824057543, 173.182049720424, 170.940897197153,
			177.823031925273, 183.621024712236, 178.774574166082]
		)
	)
);
dt << select where( Is Missing( Sum( dt[Row(), Index( 3, 11 )] ) ) & dt:BP 8W == ""  );
					
				
			
			
				
	Jim