"Query processor ran out of internal resources and could not produce a query plan" for MERGE with 2,600 records and one key field

Question

So I'm writing a Visual Studio SQL database project for an existing database.

I'm generating simple merge scripts per table for standing data, existing data so on and so forth. It's been relatively straight forward until I come to one particular table which is giving me the error in the title.

Now, if this was a complex query I'd understand, but it's not, it has one key field with a clustered index and no complex operations. I have tried removing all of the ISNULL checks from the MATCHED check after the first AND and it still gives me the same error. I don't understand!

They key is [my_table_code], the first column. Here is the bulk of the query with only the first row for clarity.

MERGE INTO [my_table] AS Target
USING (VALUES
  (N'00001L',N'20160425',N'20160425',N'132011',N'DMTEAM',N'C',N'Name',N'F',365,0,N'19790702',N'20130418',N'20130418',N'20130418',N'20130418',N'',0.0,0.0,0,N'GBP',1.0,N'19790702',N'N',N'N',0,0,0,0,N'Y',N'SLAC Life Series 1',N'19790703',365,N'UK',-1,N'N',N'H',N'N',0,N'',N'ALL',N'10000101',N'',0,0,N'0',N'N',N'N',0.000000000000000e+000,N'',N'E',365,0,0,N'N',365,0,0,N'N',0,0,N'',N'',0,N'',N'DEF',N'',N'',0,0,N'',N'',-1,N'   ',N'      ',N'   ',N' ',N'          ',N'E',N'       ',N'',N'          ',N'       ',N' ',0,1.5,4.5,7.5,0.0,0,N'0',N'0')
 -- 2600 rows more
) AS Source ([my_table_code],[my_table_create_date],[my_table_last_updt_date],[my_table_last_updt_time],[my_table_last_updt_userid],[my_table_record_status],[my_table_name],[my_table_next_or_last_price],[my_table_pricing_frequency],[my_table_sell_pricing_frequency],[my_table_commenced_date],[my_table_closed_date],[my_table_closed_for_newbus_date],[my_table_closed_for_spi_date],[my_table_closed_for_money_date],[my_table_category],[my_table_spread_relationship],[my_table_management_charge],[my_table_sellout_period_mths],[my_table_currency],[my_table_price_tolerance],[my_table_initial_price_date],[my_table_last_date_in_period],[my_table_sell_last_date_in_period],[my_table_last_day_in_period],[my_table_sell_last_day_in_period],[my_table_same_day_in_period],[my_table_sell_same_day_in_period],[my_table_use_working_days],[my_table_external_id],[my_table_post_initial_price_date],[my_table_price_applies_frequency],[my_table_price_country_code],[my_table_non_working_price_days_adj],[my_table_pricing_calendar],[my_table_risk_profile],[my_table_pay_dividend],[my_table_dividend_frequency],[my_table_sedol],[my_table_type],[my_table_strike_date],[my_table_maturity_date],[my_table_amc_basis_no],[my_table_coupon_select_id],[my_table_coupon_defaults],[my_table_whole_units],[my_table_clone_by_policy],[my_table_initial_clone_price],[my_table_price_base_calc_date],[my_table_group],[my_table_disinv_notice_freq],[my_table_disinv_notice_value],[my_table_disinv_same_day_in_period],[my_table_disinv_notice_last_date],[my_table_trade_cutoff_freq],[my_table_trade_cutoff_value],[my_table_trade_cutoff_same_day_in_period],[my_table_trade_cutoff_last_date],[my_table_expected_delay_rules],[my_table_settlement_days],[my_table_bid_offer_exception_rules],[my_table_holding_fund_id],[my_table_timeout_days],[my_table_price_valuation_basis],[my_table_classification],[my_table_target_days],[my_table_sell_target_days],[my_table_disinv_same_day_period_skip],[my_table_trade_cutoff_same_day_period_skip],[my_table_equity_sector],[my_table_client_classification],[my_table_max_decimal_places],[my_table_rounding_method],[my_table_closing_time],[my_table_rounding_direction],[my_table_use_external_WS],[my_table_gl_code],[my_table_asset_class],[my_table_grouping],[my_table_factsheet_url],[my_table_aladdin_ticker],[my_table_manager],[my_table_use_notice_for_backdates],[my_table_business_date_delay],[my_table_growth_low],[my_table_growth_med],[my_table_growth_high],[my_table_growth_SMPI],[my_table_instruction_file_decimal_places],[my_table_suspend_start_date],[my_table_suspend_end_date])
ON (Target.[my_table_code] = Source.[my_table_code])
WHEN MATCHED AND (
    NULLIF(Source.[my_table_create_date], Target.[my_table_create_date]) IS NOT NULL OR NULLIF(Target.[my_table_create_date], Source.[my_table_create_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_last_updt_date], Target.[my_table_last_updt_date]) IS NOT NULL OR NULLIF(Target.[my_table_last_updt_date], Source.[my_table_last_updt_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_last_updt_time], Target.[my_table_last_updt_time]) IS NOT NULL OR NULLIF(Target.[my_table_last_updt_time], Source.[my_table_last_updt_time]) IS NOT NULL OR 
    NULLIF(Source.[my_table_last_updt_userid], Target.[my_table_last_updt_userid]) IS NOT NULL OR NULLIF(Target.[my_table_last_updt_userid], Source.[my_table_last_updt_userid]) IS NOT NULL OR 
    NULLIF(Source.[my_table_record_status], Target.[my_table_record_status]) IS NOT NULL OR NULLIF(Target.[my_table_record_status], Source.[my_table_record_status]) IS NOT NULL OR 
    NULLIF(Source.[my_table_name], Target.[my_table_name]) IS NOT NULL OR NULLIF(Target.[my_table_name], Source.[my_table_name]) IS NOT NULL OR 
    NULLIF(Source.[my_table_next_or_last_price], Target.[my_table_next_or_last_price]) IS NOT NULL OR NULLIF(Target.[my_table_next_or_last_price], Source.[my_table_next_or_last_price]) IS NOT NULL OR 
    NULLIF(Source.[my_table_pricing_frequency], Target.[my_table_pricing_frequency]) IS NOT NULL OR NULLIF(Target.[my_table_pricing_frequency], Source.[my_table_pricing_frequency]) IS NOT NULL OR 
    NULLIF(Source.[my_table_sell_pricing_frequency], Target.[my_table_sell_pricing_frequency]) IS NOT NULL OR NULLIF(Target.[my_table_sell_pricing_frequency], Source.[my_table_sell_pricing_frequency]) IS NOT NULL OR 
    NULLIF(Source.[my_table_commenced_date], Target.[my_table_commenced_date]) IS NOT NULL OR NULLIF(Target.[my_table_commenced_date], Source.[my_table_commenced_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_closed_date], Target.[my_table_closed_date]) IS NOT NULL OR NULLIF(Target.[my_table_closed_date], Source.[my_table_closed_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_closed_for_newbus_date], Target.[my_table_closed_for_newbus_date]) IS NOT NULL OR NULLIF(Target.[my_table_closed_for_newbus_date], Source.[my_table_closed_for_newbus_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_closed_for_spi_date], Target.[my_table_closed_for_spi_date]) IS NOT NULL OR NULLIF(Target.[my_table_closed_for_spi_date], Source.[my_table_closed_for_spi_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_closed_for_money_date], Target.[my_table_closed_for_money_date]) IS NOT NULL OR NULLIF(Target.[my_table_closed_for_money_date], Source.[my_table_closed_for_money_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_category], Target.[my_table_category]) IS NOT NULL OR NULLIF(Target.[my_table_category], Source.[my_table_category]) IS NOT NULL OR 
    NULLIF(Source.[my_table_spread_relationship], Target.[my_table_spread_relationship]) IS NOT NULL OR NULLIF(Target.[my_table_spread_relationship], Source.[my_table_spread_relationship]) IS NOT NULL OR 
    NULLIF(Source.[my_table_management_charge], Target.[my_table_management_charge]) IS NOT NULL OR NULLIF(Target.[my_table_management_charge], Source.[my_table_management_charge]) IS NOT NULL OR 
    NULLIF(Source.[my_table_sellout_period_mths], Target.[my_table_sellout_period_mths]) IS NOT NULL OR NULLIF(Target.[my_table_sellout_period_mths], Source.[my_table_sellout_period_mths]) IS NOT NULL OR 
    NULLIF(Source.[my_table_currency], Target.[my_table_currency]) IS NOT NULL OR NULLIF(Target.[my_table_currency], Source.[my_table_currency]) IS NOT NULL OR 
    NULLIF(Source.[my_table_price_tolerance], Target.[my_table_price_tolerance]) IS NOT NULL OR NULLIF(Target.[my_table_price_tolerance], Source.[my_table_price_tolerance]) IS NOT NULL OR 
    NULLIF(Source.[my_table_initial_price_date], Target.[my_table_initial_price_date]) IS NOT NULL OR NULLIF(Target.[my_table_initial_price_date], Source.[my_table_initial_price_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_last_date_in_period], Target.[my_table_last_date_in_period]) IS NOT NULL OR NULLIF(Target.[my_table_last_date_in_period], Source.[my_table_last_date_in_period]) IS NOT NULL OR 
    NULLIF(Source.[my_table_sell_last_date_in_period], Target.[my_table_sell_last_date_in_period]) IS NOT NULL OR NULLIF(Target.[my_table_sell_last_date_in_period], Source.[my_table_sell_last_date_in_period]) IS NOT NULL OR 
    NULLIF(Source.[my_table_last_day_in_period], Target.[my_table_last_day_in_period]) IS NOT NULL OR NULLIF(Target.[my_table_last_day_in_period], Source.[my_table_last_day_in_period]) IS NOT NULL OR 
    NULLIF(Source.[my_table_sell_last_day_in_period], Target.[my_table_sell_last_day_in_period]) IS NOT NULL OR NULLIF(Target.[my_table_sell_last_day_in_period], Source.[my_table_sell_last_day_in_period]) IS NOT NULL OR 
    NULLIF(Source.[my_table_same_day_in_period], Target.[my_table_same_day_in_period]) IS NOT NULL OR NULLIF(Target.[my_table_same_day_in_period], Source.[my_table_same_day_in_period]) IS NOT NULL OR 
    NULLIF(Source.[my_table_sell_same_day_in_period], Target.[my_table_sell_same_day_in_period]) IS NOT NULL OR NULLIF(Target.[my_table_sell_same_day_in_period], Source.[my_table_sell_same_day_in_period]) IS NOT NULL OR 
    NULLIF(Source.[my_table_use_working_days], Target.[my_table_use_working_days]) IS NOT NULL OR NULLIF(Target.[my_table_use_working_days], Source.[my_table_use_working_days]) IS NOT NULL OR 
    NULLIF(Source.[my_table_external_id], Target.[my_table_external_id]) IS NOT NULL OR NULLIF(Target.[my_table_external_id], Source.[my_table_external_id]) IS NOT NULL OR 
    NULLIF(Source.[my_table_post_initial_price_date], Target.[my_table_post_initial_price_date]) IS NOT NULL OR NULLIF(Target.[my_table_post_initial_price_date], Source.[my_table_post_initial_price_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_price_applies_frequency], Target.[my_table_price_applies_frequency]) IS NOT NULL OR NULLIF(Target.[my_table_price_applies_frequency], Source.[my_table_price_applies_frequency]) IS NOT NULL OR 
    NULLIF(Source.[my_table_price_country_code], Target.[my_table_price_country_code]) IS NOT NULL OR NULLIF(Target.[my_table_price_country_code], Source.[my_table_price_country_code]) IS NOT NULL OR 
    NULLIF(Source.[my_table_non_working_price_days_adj], Target.[my_table_non_working_price_days_adj]) IS NOT NULL OR NULLIF(Target.[my_table_non_working_price_days_adj], Source.[my_table_non_working_price_days_adj]) IS NOT NULL OR 
    NULLIF(Source.[my_table_pricing_calendar], Target.[my_table_pricing_calendar]) IS NOT NULL OR NULLIF(Target.[my_table_pricing_calendar], Source.[my_table_pricing_calendar]) IS NOT NULL OR 
    NULLIF(Source.[my_table_risk_profile], Target.[my_table_risk_profile]) IS NOT NULL OR NULLIF(Target.[my_table_risk_profile], Source.[my_table_risk_profile]) IS NOT NULL OR 
    NULLIF(Source.[my_table_pay_dividend], Target.[my_table_pay_dividend]) IS NOT NULL OR NULLIF(Target.[my_table_pay_dividend], Source.[my_table_pay_dividend]) IS NOT NULL OR 
    NULLIF(Source.[my_table_dividend_frequency], Target.[my_table_dividend_frequency]) IS NOT NULL OR NULLIF(Target.[my_table_dividend_frequency], Source.[my_table_dividend_frequency]) IS NOT NULL OR 
    NULLIF(Source.[my_table_sedol], Target.[my_table_sedol]) IS NOT NULL OR NULLIF(Target.[my_table_sedol], Source.[my_table_sedol]) IS NOT NULL OR 
    NULLIF(Source.[my_table_type], Target.[my_table_type]) IS NOT NULL OR NULLIF(Target.[my_table_type], Source.[my_table_type]) IS NOT NULL OR 
    NULLIF(Source.[my_table_strike_date], Target.[my_table_strike_date]) IS NOT NULL OR NULLIF(Target.[my_table_strike_date], Source.[my_table_strike_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_maturity_date], Target.[my_table_maturity_date]) IS NOT NULL OR NULLIF(Target.[my_table_maturity_date], Source.[my_table_maturity_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_amc_basis_no], Target.[my_table_amc_basis_no]) IS NOT NULL OR NULLIF(Target.[my_table_amc_basis_no], Source.[my_table_amc_basis_no]) IS NOT NULL OR 
    NULLIF(Source.[my_table_coupon_select_id], Target.[my_table_coupon_select_id]) IS NOT NULL OR NULLIF(Target.[my_table_coupon_select_id], Source.[my_table_coupon_select_id]) IS NOT NULL OR 
    NULLIF(Source.[my_table_coupon_defaults], Target.[my_table_coupon_defaults]) IS NOT NULL OR NULLIF(Target.[my_table_coupon_defaults], Source.[my_table_coupon_defaults]) IS NOT NULL OR 
    NULLIF(Source.[my_table_whole_units], Target.[my_table_whole_units]) IS NOT NULL OR NULLIF(Target.[my_table_whole_units], Source.[my_table_whole_units]) IS NOT NULL OR 
    NULLIF(Source.[my_table_clone_by_policy], Target.[my_table_clone_by_policy]) IS NOT NULL OR NULLIF(Target.[my_table_clone_by_policy], Source.[my_table_clone_by_policy]) IS NOT NULL OR 
    NULLIF(Source.[my_table_initial_clone_price], Target.[my_table_initial_clone_price]) IS NOT NULL OR NULLIF(Target.[my_table_initial_clone_price], Source.[my_table_initial_clone_price]) IS NOT NULL OR 
    NULLIF(Source.[my_table_price_base_calc_date], Target.[my_table_price_base_calc_date]) IS NOT NULL OR NULLIF(Target.[my_table_price_base_calc_date], Source.[my_table_price_base_calc_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_group], Target.[my_table_group]) IS NOT NULL OR NULLIF(Target.[my_table_group], Source.[my_table_group]) IS NOT NULL OR 
    NULLIF(Source.[my_table_disinv_notice_freq], Target.[my_table_disinv_notice_freq]) IS NOT NULL OR NULLIF(Target.[my_table_disinv_notice_freq], Source.[my_table_disinv_notice_freq]) IS NOT NULL OR 
    NULLIF(Source.[my_table_disinv_notice_value], Target.[my_table_disinv_notice_value]) IS NOT NULL OR NULLIF(Target.[my_table_disinv_notice_value], Source.[my_table_disinv_notice_value]) IS NOT NULL OR 
    NULLIF(Source.[my_table_disinv_same_day_in_period], Target.[my_table_disinv_same_day_in_period]) IS NOT NULL OR NULLIF(Target.[my_table_disinv_same_day_in_period], Source.[my_table_disinv_same_day_in_period]) IS NOT NULL OR 
    NULLIF(Source.[my_table_disinv_notice_last_date], Target.[my_table_disinv_notice_last_date]) IS NOT NULL OR NULLIF(Target.[my_table_disinv_notice_last_date], Source.[my_table_disinv_notice_last_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_trade_cutoff_freq], Target.[my_table_trade_cutoff_freq]) IS NOT NULL OR NULLIF(Target.[my_table_trade_cutoff_freq], Source.[my_table_trade_cutoff_freq]) IS NOT NULL OR 
    NULLIF(Source.[my_table_trade_cutoff_value], Target.[my_table_trade_cutoff_value]) IS NOT NULL OR NULLIF(Target.[my_table_trade_cutoff_value], Source.[my_table_trade_cutoff_value]) IS NOT NULL OR 
    NULLIF(Source.[my_table_trade_cutoff_same_day_in_period], Target.[my_table_trade_cutoff_same_day_in_period]) IS NOT NULL OR NULLIF(Target.[my_table_trade_cutoff_same_day_in_period], Source.[my_table_trade_cutoff_same_day_in_period]) IS NOT NULL OR 
    NULLIF(Source.[my_table_trade_cutoff_last_date], Target.[my_table_trade_cutoff_last_date]) IS NOT NULL OR NULLIF(Target.[my_table_trade_cutoff_last_date], Source.[my_table_trade_cutoff_last_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_expected_delay_rules], Target.[my_table_expected_delay_rules]) IS NOT NULL OR NULLIF(Target.[my_table_expected_delay_rules], Source.[my_table_expected_delay_rules]) IS NOT NULL OR 
    NULLIF(Source.[my_table_settlement_days], Target.[my_table_settlement_days]) IS NOT NULL OR NULLIF(Target.[my_table_settlement_days], Source.[my_table_settlement_days]) IS NOT NULL OR 
    NULLIF(Source.[my_table_bid_offer_exception_rules], Target.[my_table_bid_offer_exception_rules]) IS NOT NULL OR NULLIF(Target.[my_table_bid_offer_exception_rules], Source.[my_table_bid_offer_exception_rules]) IS NOT NULL OR 
    NULLIF(Source.[my_table_holding_fund_id], Target.[my_table_holding_fund_id]) IS NOT NULL OR NULLIF(Target.[my_table_holding_fund_id], Source.[my_table_holding_fund_id]) IS NOT NULL OR 
    NULLIF(Source.[my_table_timeout_days], Target.[my_table_timeout_days]) IS NOT NULL OR NULLIF(Target.[my_table_timeout_days], Source.[my_table_timeout_days]) IS NOT NULL OR 
    NULLIF(Source.[my_table_price_valuation_basis], Target.[my_table_price_valuation_basis]) IS NOT NULL OR NULLIF(Target.[my_table_price_valuation_basis], Source.[my_table_price_valuation_basis]) IS NOT NULL OR 
    NULLIF(Source.[my_table_classification], Target.[my_table_classification]) IS NOT NULL OR NULLIF(Target.[my_table_classification], Source.[my_table_classification]) IS NOT NULL OR 
    NULLIF(Source.[my_table_target_days], Target.[my_table_target_days]) IS NOT NULL OR NULLIF(Target.[my_table_target_days], Source.[my_table_target_days]) IS NOT NULL OR 
    NULLIF(Source.[my_table_sell_target_days], Target.[my_table_sell_target_days]) IS NOT NULL OR NULLIF(Target.[my_table_sell_target_days], Source.[my_table_sell_target_days]) IS NOT NULL OR 
    NULLIF(Source.[my_table_disinv_same_day_period_skip], Target.[my_table_disinv_same_day_period_skip]) IS NOT NULL OR NULLIF(Target.[my_table_disinv_same_day_period_skip], Source.[my_table_disinv_same_day_period_skip]) IS NOT NULL OR 
    NULLIF(Source.[my_table_trade_cutoff_same_day_period_skip], Target.[my_table_trade_cutoff_same_day_period_skip]) IS NOT NULL OR NULLIF(Target.[my_table_trade_cutoff_same_day_period_skip], Source.[my_table_trade_cutoff_same_day_period_skip]) IS NOT NULL OR 
    NULLIF(Source.[my_table_equity_sector], Target.[my_table_equity_sector]) IS NOT NULL OR NULLIF(Target.[my_table_equity_sector], Source.[my_table_equity_sector]) IS NOT NULL OR 
    NULLIF(Source.[my_table_client_classification], Target.[my_table_client_classification]) IS NOT NULL OR NULLIF(Target.[my_table_client_classification], Source.[my_table_client_classification]) IS NOT NULL OR 
    NULLIF(Source.[my_table_max_decimal_places], Target.[my_table_max_decimal_places]) IS NOT NULL OR NULLIF(Target.[my_table_max_decimal_places], Source.[my_table_max_decimal_places]) IS NOT NULL OR 
    NULLIF(Source.[my_table_rounding_method], Target.[my_table_rounding_method]) IS NOT NULL OR NULLIF(Target.[my_table_rounding_method], Source.[my_table_rounding_method]) IS NOT NULL OR 
    NULLIF(Source.[my_table_closing_time], Target.[my_table_closing_time]) IS NOT NULL OR NULLIF(Target.[my_table_closing_time], Source.[my_table_closing_time]) IS NOT NULL OR 
    NULLIF(Source.[my_table_rounding_direction], Target.[my_table_rounding_direction]) IS NOT NULL OR NULLIF(Target.[my_table_rounding_direction], Source.[my_table_rounding_direction]) IS NOT NULL OR 
    NULLIF(Source.[my_table_use_external_WS], Target.[my_table_use_external_WS]) IS NOT NULL OR NULLIF(Target.[my_table_use_external_WS], Source.[my_table_use_external_WS]) IS NOT NULL OR 
    NULLIF(Source.[my_table_gl_code], Target.[my_table_gl_code]) IS NOT NULL OR NULLIF(Target.[my_table_gl_code], Source.[my_table_gl_code]) IS NOT NULL OR 
    NULLIF(Source.[my_table_asset_class], Target.[my_table_asset_class]) IS NOT NULL OR NULLIF(Target.[my_table_asset_class], Source.[my_table_asset_class]) IS NOT NULL OR 
    NULLIF(Source.[my_table_grouping], Target.[my_table_grouping]) IS NOT NULL OR NULLIF(Target.[my_table_grouping], Source.[my_table_grouping]) IS NOT NULL OR 
    NULLIF(Source.[my_table_factsheet_url], Target.[my_table_factsheet_url]) IS NOT NULL OR NULLIF(Target.[my_table_factsheet_url], Source.[my_table_factsheet_url]) IS NOT NULL OR 
    NULLIF(Source.[my_table_aladdin_ticker], Target.[my_table_aladdin_ticker]) IS NOT NULL OR NULLIF(Target.[my_table_aladdin_ticker], Source.[my_table_aladdin_ticker]) IS NOT NULL OR 
    NULLIF(Source.[my_table_manager], Target.[my_table_manager]) IS NOT NULL OR NULLIF(Target.[my_table_manager], Source.[my_table_manager]) IS NOT NULL OR 
    NULLIF(Source.[my_table_use_notice_for_backdates], Target.[my_table_use_notice_for_backdates]) IS NOT NULL OR NULLIF(Target.[my_table_use_notice_for_backdates], Source.[my_table_use_notice_for_backdates]) IS NOT NULL OR 
    NULLIF(Source.[my_table_business_date_delay], Target.[my_table_business_date_delay]) IS NOT NULL OR NULLIF(Target.[my_table_business_date_delay], Source.[my_table_business_date_delay]) IS NOT NULL OR 
    NULLIF(Source.[my_table_growth_low], Target.[my_table_growth_low]) IS NOT NULL OR NULLIF(Target.[my_table_growth_low], Source.[my_table_growth_low]) IS NOT NULL OR 
    NULLIF(Source.[my_table_growth_med], Target.[my_table_growth_med]) IS NOT NULL OR NULLIF(Target.[my_table_growth_med], Source.[my_table_growth_med]) IS NOT NULL OR 
    NULLIF(Source.[my_table_growth_high], Target.[my_table_growth_high]) IS NOT NULL OR NULLIF(Target.[my_table_growth_high], Source.[my_table_growth_high]) IS NOT NULL OR 
    NULLIF(Source.[my_table_growth_SMPI], Target.[my_table_growth_SMPI]) IS NOT NULL OR NULLIF(Target.[my_table_growth_SMPI], Source.[my_table_growth_SMPI]) IS NOT NULL OR 
    NULLIF(Source.[my_table_instruction_file_decimal_places], Target.[my_table_instruction_file_decimal_places]) IS NOT NULL OR NULLIF(Target.[my_table_instruction_file_decimal_places], Source.[my_table_instruction_file_decimal_places]) IS NOT NULL OR 
    NULLIF(Source.[my_table_suspend_start_date], Target.[my_table_suspend_start_date]) IS NOT NULL OR NULLIF(Target.[my_table_suspend_start_date], Source.[my_table_suspend_start_date]) IS NOT NULL OR 
    NULLIF(Source.[my_table_suspend_end_date], Target.[my_table_suspend_end_date]) IS NOT NULL OR NULLIF(Target.[my_table_suspend_end_date], Source.[my_table_suspend_end_date]) IS NOT NULL ) THEN

 UPDATE SET
  [my_table_create_date] = Source.[my_table_create_date], 
  [my_table_last_updt_date] = Source.[my_table_last_updt_date], 
  -- All fields listed in order.
  [my_table_suspend_end_date] = Source.[my_table_suspend_end_date]
WHEN NOT MATCHED BY TARGET THEN
 INSERT([my_table_code],[my_table_create_date],[my_table_last_updt_date],[my_table_last_updt_time],[my_table_last_updt_userid],[my_table_record_status],[my_table_name],[my_table_next_or_last_price],[my_table_pricing_frequency],[my_table_sell_pricing_frequency],[my_table_commenced_date],[my_table_closed_date],[my_table_closed_for_newbus_date],[my_table_closed_for_spi_date],[my_table_closed_for_money_date],[my_table_category],[my_table_spread_relationship],[my_table_management_charge],[my_table_sellout_period_mths],[my_table_currency],[my_table_price_tolerance],[my_table_initial_price_date],[my_table_last_date_in_period],[my_table_sell_last_date_in_period],[my_table_last_day_in_period],[my_table_sell_last_day_in_period],[my_table_same_day_in_period],[my_table_sell_same_day_in_period],[my_table_use_working_days],[my_table_external_id],[my_table_post_initial_price_date],[my_table_price_applies_frequency],[my_table_price_country_code],[my_table_non_working_price_days_adj],[my_table_pricing_calendar],[my_table_risk_profile],[my_table_pay_dividend],[my_table_dividend_frequency],[my_table_sedol],[my_table_type],[my_table_strike_date],[my_table_maturity_date],[my_table_amc_basis_no],[my_table_coupon_select_id],[my_table_coupon_defaults],[my_table_whole_units],[my_table_clone_by_policy],[my_table_initial_clone_price],[my_table_price_base_calc_date],[my_table_group],[my_table_disinv_notice_freq],[my_table_disinv_notice_value],[my_table_disinv_same_day_in_period],[my_table_disinv_notice_last_date],[my_table_trade_cutoff_freq],[my_table_trade_cutoff_value],[my_table_trade_cutoff_same_day_in_period],[my_table_trade_cutoff_last_date],[my_table_expected_delay_rules],[my_table_settlement_days],[my_table_bid_offer_exception_rules],[my_table_holding_fund_id],[my_table_timeout_days],[my_table_price_valuation_basis],[my_table_classification],[my_table_target_days],[my_table_sell_target_days],[my_table_disinv_same_day_period_skip],[my_table_trade_cutoff_same_day_period_skip],[my_table_equity_sector],[my_table_client_classification],[my_table_max_decimal_places],[my_table_rounding_method],[my_table_closing_time],[my_table_rounding_direction],[my_table_use_external_WS],[my_table_gl_code],[my_table_asset_class],[my_table_grouping],[my_table_factsheet_url],[my_table_aladdin_ticker],[my_table_manager],[my_table_use_notice_for_backdates],[my_table_business_date_delay],[my_table_growth_low],[my_table_growth_med],[my_table_growth_high],[my_table_growth_SMPI],[my_table_instruction_file_decimal_places],[my_table_suspend_start_date],[my_table_suspend_end_date])
 VALUES(Source.[my_table_code],Source.[my_table_create_date],Source.[my_table_last_updt_date],Source.[my_table_last_updt_time],Source.[my_table_last_updt_userid],Source.[my_table_record_status],Source.[my_table_name],Source.[my_table_next_or_last_price],Source.[my_table_pricing_frequency],Source.[my_table_sell_pricing_frequency],Source.[my_table_commenced_date],Source.[my_table_closed_date],Source.[my_table_closed_for_newbus_date],Source.[my_table_closed_for_spi_date],Source.[my_table_closed_for_money_date],Source.[my_table_category],Source.[my_table_spread_relationship],Source.[my_table_management_charge],Source.[my_table_sellout_period_mths],Source.[my_table_currency],Source.[my_table_price_tolerance],Source.[my_table_initial_price_date],Source.[my_table_last_date_in_period],Source.[my_table_sell_last_date_in_period],Source.[my_table_last_day_in_period],Source.[my_table_sell_last_day_in_period],Source.[my_table_same_day_in_period],Source.[my_table_sell_same_day_in_period],Source.[my_table_use_working_days],Source.[my_table_external_id],Source.[my_table_post_initial_price_date],Source.[my_table_price_applies_frequency],Source.[my_table_price_country_code],Source.[my_table_non_working_price_days_adj],Source.[my_table_pricing_calendar],Source.[my_table_risk_profile],Source.[my_table_pay_dividend],Source.[my_table_dividend_frequency],Source.[my_table_sedol],Source.[my_table_type],Source.[my_table_strike_date],Source.[my_table_maturity_date],Source.[my_table_amc_basis_no],Source.[my_table_coupon_select_id],Source.[my_table_coupon_defaults],Source.[my_table_whole_units],Source.[my_table_clone_by_policy],Source.[my_table_initial_clone_price],Source.[my_table_price_base_calc_date],Source.[my_table_group],Source.[my_table_disinv_notice_freq],Source.[my_table_disinv_notice_value],Source.[my_table_disinv_same_day_in_period],Source.[my_table_disinv_notice_last_date],Source.[my_table_trade_cutoff_freq],Source.[my_table_trade_cutoff_value],Source.[my_table_trade_cutoff_same_day_in_period],Source.[my_table_trade_cutoff_last_date],Source.[my_table_expected_delay_rules],Source.[my_table_settlement_days],Source.[my_table_bid_offer_exception_rules],Source.[my_table_holding_fund_id],Source.[my_table_timeout_days],Source.[my_table_price_valuation_basis],Source.[my_table_classification],Source.[my_table_target_days],Source.[my_table_sell_target_days],Source.[my_table_disinv_same_day_period_skip],Source.[my_table_trade_cutoff_same_day_period_skip],Source.[my_table_equity_sector],Source.[my_table_client_classification],Source.[my_table_max_decimal_places],Source.[my_table_rounding_method],Source.[my_table_closing_time],Source.[my_table_rounding_direction],Source.[my_table_use_external_WS],Source.[my_table_gl_code],Source.[my_table_asset_class],Source.[my_table_grouping],Source.[my_table_factsheet_url],Source.[my_table_aladdin_ticker],Source.[my_table_manager],Source.[my_table_use_notice_for_backdates],Source.[my_table_business_date_delay],Source.[my_table_growth_low],Source.[my_table_growth_med],Source.[my_table_growth_high],Source.[my_table_growth_SMPI],Source.[my_table_instruction_file_decimal_places],Source.[my_table_suspend_start_date],Source.[my_table_suspend_end_date])
WHEN NOT MATCHED BY SOURCE THEN 
 DELETE
;
GO
DECLARE @mergeError int
 , @mergeCount int
SELECT @mergeError = @@ERROR, @mergeCount = @@ROWCOUNT
IF @mergeError != 0
 BEGIN
 PRINT 'ERROR OCCURRED IN MERGE FOR [my_table]. Rows affected: ' + CAST(@mergeCount AS VARCHAR(100)); -- SQL should always return zero rows affected
 END
ELSE
 BEGIN
 PRINT '[my_table] rows affected by MERGE: ' + CAST(@mergeCount AS VARCHAR(100));
 END
GO    

EDIT: Ok so removing 2508 rows it works in seconds. I don't know enough about merge scripts to know why the amount of rows would affect this.

Answer 1

Inserting the values into a temp table first and referencing that in the merge fixed it.

Also, replacing the long list of NULLIF with:

WHEN MATCHED AND EXISTS
(
SELECT Source.*
EXCEPT
SELECT Target.*
)   

worked to speed it up.