Alternative in SQL Server CASE

Question

Ich habe die folgenden beiden Tabellen:..

CREATE TABLE [dbo].[TAB1](
    [COIL_ID] [varchar](25) NOT NULL, 
    [COIL_DATE] [datetime] NULL, 
    [GRADE] [float] NULL, 
    [QUALITY] [float] NULL, 
    [FURNACE_NUM] [float] NULL, 
    [FM_GAUGE] [float] NULL, 
    [FM_WIDTH] [float] NULL, 
    [FINTEMP_AIM] [float] NULL, 
    [SLAB_GAUGE] [float] NULL, 
    [SLAB_WIDTH] [float] NULL, 
    [SLAB_LENGTH] [float] NULL, 
    [DO_TEMP] [float] NULL, 
    [GAP_REFERENCE_PR1_1] [float] NULL, 
    [GAP_REFERENCE_PR1_2] [float] NULL, 
    [GAP_REFERENCE_PR1_3] [float] NULL, 
    [GAP_REFERENCE_PR1_4] [float] NULL, 
    [GAP_REFERENCE_PR1_5] [float] NULL, 
    [GAP_REFERENCE_PR1_6] [float] NULL, 
    [GAP_REFERENCE_PR1_7] [float] NULL, 
    [GAP_REFERENCE_PR1_8] [float] NULL, 
    [GAP_REFERENCE_PR1_9] [float] NULL, 
    [GAP_REFERENCE_PR1_10] [float] NULL, 
    [GAP_REFERENCE_PR1_11] [float] NULL, 
    [GAP_REFERENCE_PR1_12] [float] NULL, 
    [GAP_REFERENCE_PR1_13] [float] NULL, 
    [GAP_REFERENCE_PR1_14] [float] NULL, 
    [GAP_REFERENCE_PR1_15] [float] NULL, 
    [GAP_REFERENCE_PR1_16] [float] NULL, 
    [GAP_REFERENCE_PR1_17] [float] NULL, 
    [GAP_REFERENCE_PR1_18] [float] NULL, 
    [GAP_REFERENCE_PR1_19] [float] NULL, 
    [GAP_REFERENCE_PR1_20] [float] NULL, 
    [GAP_REFERENCE_PR1_21] [float] NULL, 
    [GAP_REFERENCE_PR1_22] [float] NULL, 
    [GAP_REFERENCE_PR1_23] [float] NULL, 
    [GAP_REFERENCE_PR1_24] [float] NULL, 
    [GAP_REFERENCE_PR1_25] [float] NULL 
) 


CREATE TABLE [dbo].[TAB2](
    [COIL_ID] [varchar](25) NOT NULL, 
    [_SegmentNr] [int] NOT NULL, 
    [HRM Metal In Mill] [real] NULL, 
    [HRM Screws Homed] [real] NULL, 
    [HRM Tracking Current Pass Number] [real] NULL, 
    [Topmotor_ArmCur] [real] NULL, 
    [Max_Topmtr_Armcur_pass] [real] NULL, 
    [Botmotor_ArmCur] [real] NULL, 
    [Max_Botmtr_Armcur_pass] [real] NULL, 
    [SPEED] [real] NULL, 
    [POWER] [real] NULL, 
    [TEMP] [real] NULL, 
    [T_Load] [real] NULL, 
    [D_Load] [real] NULL, 
    [PosFb] [real] NULL, 
    [Dif_Pos] [real] NULL, 
    [Guide_Entry] [real] NULL, 
    [Guide_Exit] [real] NULL, 
    [Thread_Achi] [real] NULL 
) 

Es wird eine Zeile in [dbo] [TAB1] für eine coild-ID und mehrere Zeilen in [dbo] [TAB2 ].

Die löschte I müssen Sie wie folgt vor:

COIL-ID HRM-Tracking-Current-Pass-Number  GAP 
1    1        value of GAP_REFERENCE_PR1_1      
1    2        value of GAP_REFERENCE_PR1_2       
1    3        value of GAP_REFERENCE_PR1_3 

ich zur Zeit den folgenden Code verwende:

select a.coil_id Coil_ID, b.[HRM Tracking Current Pass Number] , 
max(case b.[HRM Tracking Current Pass Number] 
when 1 THEN a.EXIT_GAUGE_PR1_1 
when 2 THEN a.EXIT_GAUGE_PR1_2 
when 3 THEN a.EXIT_GAUGE_PR1_3 
when 4 THEN a.EXIT_GAUGE_PR1_4 
when 5 THEN a.EXIT_GAUGE_PR1_5 
when 6 THEN a.EXIT_GAUGE_PR1_6 
when 7 THEN a.EXIT_GAUGE_PR1_7 
when 8 THEN a.EXIT_GAUGE_PR1_8 
when 9 THEN a.EXIT_GAUGE_PR1_9 
when 10 THEN a.EXIT_GAUGE_PR1_10 
when 11 THEN a.EXIT_GAUGE_PR1_11 
when 12 THEN a.EXIT_GAUGE_PR1_12 
when 13 THEN a.EXIT_GAUGE_PR1_13 
when 14 THEN a.EXIT_GAUGE_PR1_14 
when 15 THEN a.EXIT_GAUGE_PR1_15 
when 16 THEN a.EXIT_GAUGE_PR1_16 
when 17 THEN a.EXIT_GAUGE_PR1_17 
when 18 THEN a.EXIT_GAUGE_PR1_18 
when 19 THEN a.EXIT_GAUGE_PR1_19 
when 20 THEN a.EXIT_GAUGE_PR1_20 
when 21 THEN a.EXIT_GAUGE_PR1_21 
when 22 THEN a.EXIT_GAUGE_PR1_22 
when 23 THEN a.EXIT_GAUGE_PR1_23 
when 24 THEN a.EXIT_GAUGE_PR1_24 
when 25 THEN a.EXIT_GAUGE_PR1_25 
END) as EXIT_GAUGE, 

Ich möchte wissen, ob es eine effizientere Art und Weise das Schreiben der Abfrage ist.

Vielen Dank im Voraus für die Hilfe.

Answer 1

Ab SQL Server 2012 gibt es eine CHOOSE Methode:

SELECT CHOOSE (3, 'Manager', 'Director', 'Developer', 'Tester') AS Result; 

Result 
------------- 
Developer 

Also in Ihrem Fall könnten Sie wahrscheinlich es wie folgt verwendet werden:

SELECT MAX(
    CHOOSE(
     b.[HRM Tracking Current Pass Number], 
     a.EXIT_GAUGE_PR1_1, 
     a.EXIT_GAUGE_PR1_2, 
     a.EXIT_GAUGE_PR1_3, 
     ... 
    ) 
)