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问题:

I am trying to minimise the calculation / query time for the following UPDATE statement that is embedded in a stored procedure on my server...

SET @EQUIPMENT_VARIABLE = 'B1010-V001'; UPDATE EQUIPMENT e          /*24. MAX COF*/     SET e.MAX_COF = least(COF_SAFETY, COF_HEALTH, COF_ENVIRONMENT, COF_ASSETS)          /*25. RECOMMENDED RBI INTERNAL INTERVAL*/         , e.RECOMMENDED_RBI_INTERNAL_INTERVAL = (SELECT RECOMMENDED_RBI_INTERNAL_INSPECTION_INTERVAL FROM DAMAGE_MECHANISM WHERE EQUIPMENT_ID = e.EQUIPMENT_ID ORDER BY RECOMMENDED_RBI_INTERNAL_INSPECTION_INTERVAL ASC LIMIT 1)         /*26. LAST INSPECTION DATE INTERNAL*/         , e.LAST_INSPECTION_DATE_INTERNAL =     (                                                 SELECT a.LAST_INSPECTION_DATE                                                  FROM CML a LEFT JOIN CML_TYPES b ON a.CML_TYPE = b.CML_TYPE                                                 WHERE a.EQUIPMENT_ID = e.EQUIPMENT_ID AND a.STATUS NOT IN('X') AND b.INTERNAL_EXTERNAL = 'INTERNAL'                                                 ORDER BY LAST_INSPECTION_DATE DESC LIMIT 1                                                 )         /*27. NEXT INSPECTION DATE INTERNAL*/         , e.NEXT_INSPECTION_DATE_INTERNAL = DATE_ADD(e.LAST_INSPECTION_DATE_INTERNAL, INTERVAL FLOOR(RECOMMENDED_RBI_INTERNAL_INTERVAL * 365) DAY)         /*28. RECOMMENDED RBI EXTERNAL INTERVAL*/         , e.RECOMMENDED_RBI_EXTERNAL_INTERVAL = (SELECT RECOMMENDED_RBI_EXTERNAL_INSPECTION_INTERVAL FROM DAMAGE_MECHANISM WHERE EQUIPMENT_ID = e.EQUIPMENT_ID ORDER BY RECOMMENDED_RBI_EXTERNAL_INSPECTION_INTERVAL ASC LIMIT 1)         /*29. LAST INSPECTION DATE EXERNAL*/         , e.LAST_INSPECTION_DATE_EXTERNAL =     (                                                 SELECT a.LAST_INSPECTION_DATE                                                  FROM CML a LEFT JOIN CML_TYPES b ON a.CML_TYPE = b.CML_TYPE                                                 WHERE a.EQUIPMENT_ID = e.EQUIPMENT_ID AND a.STATUS NOT IN('X') AND b.INTERNAL_EXTERNAL = 'EXTERNAL'                                                 ORDER BY LAST_INSPECTION_DATE DESC LIMIT 1                                                 )         /*30. NEXT INSPECTION DATE EXTERNAL*/         , e.NEXT_INSPECTION_DATE_EXTERNAL = DATE_ADD(e.LAST_INSPECTION_DATE_EXTERNAL, INTERVAL FLOOR(RECOMMENDED_RBI_EXTERNAL_INTERVAL * 365) DAY)               /*31. END OF LIFE*/         , e.END_OF_LIFE =   (                             SELECT END_OF_LIFE                             FROM CML                             WHERE EQUIPMENT_ID = e.EQUIPMENT_ID AND STATUS NOT IN('X')                             ORDER BY END_OF_LIFE ASC LIMIT 1                             )         /*XX. REMEDIATION STATUS*/         , e.REMEDIATION_STATUS = (SELECT GROUP_CONCAT(DISTINCT(REMEDIATION_STATUS)) FROM CML WHERE EQUIPMENT_ID = e.EQUIPMENT_ID AND STATUS NOT IN('X'))         , e.REMEDIATION_STATUS =              CASE    WHEN e.REMEDIATION_STATUS IS NOT NULL                     THEN e.REMEDIATION_STATUS                     ELSE 'F'             END         /*XX. MAX ACR*/         , e.MAX_ACR = (SELECT APPLIED_CORROSION_RATE FROM CML WHERE EQUIPMENT_ID = e.EQUIPMENT_ID AND STATUS NOT IN ('X') ORDER BY APPLIED_CORROSION_RATE DESC LIMIT 1)         /*XX. MIN REMAINING LIFE*/         , e.MIN_REMAINING_LIFE = (SELECT REMAINING_LIFE_BASED_ON_ACR FROM CML WHERE EQUIPMENT_ID = e.EQUIPMENT_ID AND STATUS NOT IN ('X') ORDER BY REMAINING_LIFE_BASED_ON_ACR ASC LIMIT 1)     WHERE e.EQUIPMENT_ID like @EQUIPMENT_VARIABLE;

Any ideas on how I can improve the query structure to minimise the query time / maximise the UPDATE query performance?

** UPDATE **

Approximate number of records in each major table is as follows:

CML_TYPES: 10
REMEDIATION_STATUSES: 10
INSPECTION: 218,000
CML: 2180
DAMAGE_MECHANISM: 2180
EQUIPMENT: 218

Table database structure is provided below.

/*CREATE TABLES AND SET DATATYPES*/ /*LOOKUP TABLES TO BE ADDED FIRST SO FOREIGN KEY CONSTRAINTS CAN BE ASSIGNED CORRECTLY*/ CREATE TABLE IDMAS_VESSELS.CML_TYPES (   /*FIELD NAME*/                                  /*DATA TYPE AND RESTRICTIONS*/     `CML_TYPE`                                      VARCHAR(50),     `INTERNAL_EXTERNAL`                             enum('INTERNAL', 'EXTERNAL') default NULL,      /*PRIMARY AND FOREIGN KEY DEFINITIONS*/     PRIMARY KEY (CML_TYPE),      /*ADD TABLE INDEXES TO IMPROVE PERFORMANCE*/     INDEX CML_TYPES_INDEX (CML_TYPE)  ) ENGINE=InnoDB;  CREATE TABLE IDMAS_VESSELS.REMEDIATION_STATUSES (   /*FIELD NAME*/                                  /*DATA TYPE AND RESTRICTIONS*/     `REMEDIATION_STATUS`                            VARCHAR(1),     `DESCRIPTION`                                   VARCHAR(100),      /*PRIMARY AND FOREIGN KEY DEFINITIONS*/     PRIMARY KEY (REMEDIATION_STATUS)      /*ADD TABLE INDEXES TO IMPROVE PERFORMANCE*/     -- PRIMARY KEY INDEXED BY DEFAULT. NO OTHER INDEXES REQUIRED.  ) ENGINE=InnoDB;  CREATE TABLE IDMAS_VESSELS.EQUIPMENT (   /*FIELD NAME*/                                  /*DATA TYPE AND RESTRICTIONS*/     `EQUIPMENT_ID`                                  VARCHAR(20) NOT NULL,     `EQUIP_TYPE`                                    VARCHAR(50),     `STATUS_OF_VESSEL`                              enum('ACTIVE', 'INACTIVE') NOT NULL default 'ACTIVE',     `REMEDIATION_STATUS`                            VARCHAR(10),     `MIN_REMAINING_LIFE`                            DOUBLE,     `MAX_ACR`                                       DOUBLE,     `END_OF_LIFE`                                   DATE,     `AREA`                                          VARCHAR(50),     `EQUIP_FROM`                                    VARCHAR(50),     `EQUIP_TO`                                      VARCHAR(20),     `CONTENTS`                                      VARCHAR(50),     `COMMENTS`                                      TEXT,     `MATERIAL`                                      VARCHAR(50),     `MATERIAL_SPECIFICATION`                        VARCHAR(2),     `CORROSION_ALLOWANCE (MM)`                      DOUBLE(2,2),     `CONSTRUCTION_CODE`                             VARCHAR(20),     `DESIGN_PRESSURE_MPA`                           DOUBLE,     `DESIGN_TEMPERATURE_DEGC`                       DOUBLE,     `PID`                                           VARCHAR(20),     `DRAWING_REF`                                   VARCHAR(20),     `OPERATING_PRESSURE_KPA`                        DOUBLE,     `OPERATING_TEMP_DEGC`                           DOUBLE,     `CAPACITY_L`                                    DOUBLE,     `CAPACITY_MPA_PER_L`                            DOUBLE,     `MAXIMUM_ALLOWABLE_WORKING_PRESSURE_MPA`        DOUBLE,     `MAXIMUM_ALLOWABLE_WORKING_TEMPERATURE_DEGC`    DOUBLE,     `DESIGN_STRENGTH_MPA`                           DOUBLE,     `JOINT_EFFICIENCY`                              DOUBLE,     `COF_SAFETY`                                    INT(1),     `COF_HEALTH`                                    INT(1),     `COF_ENVIRONMENT`                               INT(1),     `COF_ASSETS`                                    INT(1),     `MAX_COF`                                       INT(1),     `HAZARD_LEVEL`                                  CHAR(1),     `CONTENTS_CLASS`                                VARCHAR(50),     `INSTALLATION_YEAR`                             DATE,     `INTERIOR_COATING`                              VARCHAR(50),     `EXTERIOR_COATING`                              VARCHAR(50),     `EXTERIOR_INSUL`                                VARCHAR(50),     `MANUFACTURER`                                  VARCHAR(50),     `MANUFACTURE_DATE`                              DATE,     `MANUFACTURE_NO`                                VARCHAR(50),     `INTERNAL_ANODES`                               VARCHAR(50),     `ASSOC_PSV`                                     VARCHAR(50),     `MAINT_ITEM_CODE`                               VARCHAR(50),     `SERV_TYPE`                                     VARCHAR(50),     `EQUIP_CLASS`                                   VARCHAR(50),     `EQUIP_SUBCLASS`                                VARCHAR(50),     `PROCESS_UNIT`                                  VARCHAR(50),     `RECOMMENDED_RBI_INTERNAL_INTERVAL`             DOUBLE,     `LAST_INSPECTION_DATE_INTERNAL`                 DATE,     `NEXT_INSPECTION_DATE_INTERNAL`                 DATE,     `RECOMMENDED_RBI_EXTERNAL_INTERVAL`             DOUBLE,     `LAST_INSPECTION_DATE_EXTERNAL`                 DATE,     `NEXT_INSPECTION_DATE_EXTERNAL`                 DATE,     `DESIGN_LIFE`                                   DOUBLE,      /*PRIMARY AND FOREIGN KEY DEFINITIONS*/     PRIMARY KEY (EQUIPMENT_ID),      /*INDEX FIELDS TO INCREASE PERFORMANCE REDUCES NUMBER OF ACCESSES (N) FROM N to LOG2(N) I.E. AN EXPONENTIAL DECREASE      *APPLYING THESE INDEXES TO PRIMARY KEY FIELDS ALSO REMOVES THE REQUIREMENT FOR THE SYSTEM TO SEARCH FOR DUPLICATES      *INDEXES ONLY INCREASE THE DISK SPACE REQUIRED OF THE DATABASE.      *ALL DATABASE SEARCHING SHOULD ALWAYS BE DONE ON THE PRIMARY KEY INDEXED FIELD.      */     INDEX EQUIPMENT_INDEX (EQUIPMENT_ID)  ) ENGINE=InnoDB;  CREATE TABLE IDMAS_VESSELS.DAMAGE_MECHANISM (   /*FIELD NAME*/                                              /*DATA TYPE AND RESTRICTIONS*/     `DAMAGE_MECHANISM_ID`                                       VARCHAR(50) NOT NULL,     `EQUIPMENT_ID`                                              VARCHAR(20),     `DESCRIPTION`                                               VARCHAR(50),     `REMEDIATION_STATUS`                                        VARCHAR(10),     `DAMAGE_MECHANISM_TYPE`                                     enum('QUALITATIVE', 'QUANTITATIVE') default NULL,     `INSPECTION_STRATEGY`                                       VARCHAR(20),     `AGE_RELATED`                                               enum('YES', 'NO') NOT NULL default 'NO',     `FEASIBLE`                                                  enum('YES', 'NO') NOT NULL default 'NO',     `NOTES_ON_FEASIBILITY`                                      TEXT,     `MIN_REMAINING_LIFE`                                        DOUBLE,     `MAX_ACR`                                                   DOUBLE,     `MINIMUM_CALCULATED_RBI_INTERVAL`                           DOUBLE,     `MAXIMUM_CRITICALITY_RATING`                                VARCHAR(20),     `RECOMMENDED_RBI_INTERNAL_INSPECTION_INTERVAL`              DOUBLE,     `LAST_INSPECTION_DATE_INTERNAL`                             DATE,     `NEXT_INSPECTION_DATE_INTERNAL`                             DATE,     `NOTES_ON_RECOMMENDED_RBI_INTERNAL_INSPECTION_INTERVAL`     TEXT,     `RECOMMENDED_RBI_EXTERNAL_INSPECTION_INTERVAL`              DOUBLE,     `LAST_INSPECTION_DATE_EXTERNAL`                             DATE,     `NEXT_INSPECTION_DATE_EXTERNAL`                             DATE,     `NOTES_ON_RECOMMENDED_RBI_EXTERNAL_INSPECTION_INTERVAL`     TEXT,      /*PRIMARY AND FOREIGN KEY DEFINITIONS*/     PRIMARY KEY (DAMAGE_MECHANISM_ID, EQUIPMENT_ID),     FOREIGN KEY (EQUIPMENT_ID) REFERENCES EQUIPMENT(EQUIPMENT_ID),      /*ADD TABLE INDEXES TO IMPROVE PERFORMANCE*/     INDEX DAMAGE_MECHANISM_INDEX (EQUIPMENT_ID, DAMAGE_MECHANISM_ID)  ) ENGINE=InnoDB;  CREATE TABLE IDMAS_VESSELS.CML (   /*FIELD NAME*/                                  /*DATA TYPE AND RESTRICTIONS*/     `CML_ID`                                        INT NOT NULL,     `CML_LOCATION`                                  VARCHAR(20),     `STATUS`                                        enum('C','X','A','U') NOT NULL default 'C',     `REMEDIATION_STATUS`                            VARCHAR(1),     `EQUIPMENT_ID`                                  VARCHAR(20),     `DAMAGE_MECHANISM_ID`                           VARCHAR(50),     `CML_TYPE`                                      VARCHAR(50),     `LAST_INSPECTION_DATE`                          DATE,     `NOMINAL_DIAMETER_MM`                           DOUBLE,     `OUTSIDE_DIAMETER_MM`                           DOUBLE,     `MEAN_DIAMETER_MM`                              DOUBLE,     `NOMINAL_WALL_THICKNESS_MM`                     DOUBLE,     `MINIMUM_REMAINING_WALL_THICKNESS_MM`           DOUBLE,     `DEPTH_OF_LOSS_FROM_NWT_MM`                     DOUBLE,     `THICKNESS_WALL_LOSS_PERCENTAGE`                DOUBLE,     `PHOTO`                                         INT,     `MINIMUM_ALLOWABLE_WALL_THICKNESS_MM`           DOUBLE,     `ACTUAL_CORROSION_RATE_MM_PER_YEAR`             DOUBLE,     `MAX_CALCULATED_CORROSION_RATE`                 DOUBLE,     `DAMAGE_LOOP_MAXIMUM_CORROSION_RATE`            DOUBLE,     `APPLIED_CORROSION_RATE`                        DOUBLE,     `APPLIED_CORROSION_RATE_NOTES_AND_ENTERED_BY`   TEXT,     `FAILURE_MODE`                                  VARCHAR(50),     `REMAINING_LIFE_BASED_ON_ACR`                   DOUBLE,     `END_OF_LIFE`                                   DATE,     `LR_LD_APPLIED`                                 DOUBLE,     `POF_APPLIED`                                   INT(1),     `DAMAGE_MECHANISM_VISUAL`                       TEXT,     `FAILURE_MODE_VISUAL`                           TEXT,     `POF_APPLIED_VISUAL`                            INT(1),     `POF_APPLIED_VISUAL_COMMENT`                    TEXT,     `CRITICALITY_RATING_VISUAL`                     INT(2),     `CRITICALITY_RATING_APPLIED`                    VARCHAR(10),     `DEGRADATION_MECHANISM`                         DOUBLE,     `RELIABLE_MONITORING`                           DOUBLE,     `MULTIPLE_INSPECTIONS`                          DOUBLE,     `CONFIDENCE_SCORE`                              DOUBLE,     `CONFIDENCE_RATING`                             VARCHAR(50),     `INSPECTION_INTERVAL_FACTOR_APPLIED`            DOUBLE,     `RISK_BASED_INSPECTION_INTERVAL_APPLIED_YEARS`  DOUBLE,     `RECOMMENDED_REMEDIATION`                       TEXT,      /*PRIMARY AND FOREIGN KEY DEFINITIONS*/     PRIMARY KEY (EQUIPMENT_ID, CML_ID),     FOREIGN KEY (EQUIPMENT_ID, DAMAGE_MECHANISM_ID) REFERENCES DAMAGE_MECHANISM(EQUIPMENT_ID, DAMAGE_MECHANISM_ID),     FOREIGN KEY (CML_TYPE) REFERENCES CML_TYPES(CML_TYPE),     FOREIGN KEY (REMEDIATION_STATUS) REFERENCES REMEDIATION_STATUSES(REMEDIATION_STATUS),      /*ADD TABLE INDEXES TO IMPROVE PERFORMANCE*/     INDEX CML_INDEX (EQUIPMENT_ID, CML_ID)  ) ENGINE=InnoDB;  CREATE TABLE IDMAS_VESSELS.INSPECTION (   /*FIELD NAME*/                                  /*DATA TYPE AND RESTRICTIONS*/     `INSPECTION_NO`                                 INT NOT NULL,     `STATUS`                                        enum('P','A','S','R') NOT NULL default 'P',     `CML_ID`                                        INT NOT NULL,     `EQUIPMENT_ID`                                  VARCHAR(20),     `INSPECTION_TYPE`                               VARCHAR(50),     `SCOPE_COMMENTS`                                TEXT,     `NOMINAL_WALL_THICKNESS`                        DOUBLE,     `MINIMUM_REMAINING_WALL_THICKNESS`              DOUBLE,     `WALL_LOSS`                                     DOUBLE,     `SERVICE_YEARS`                                 DOUBLE,     `CORROSION_RATE_ACTUAL_SHORT_TERM_MM_PER_YEAR`  DOUBLE,     `CONDITION`                                     VARCHAR(50),     `INSPECTION_DATE`                               DATE,     `NDT_REPORT_NUMBER`                             VARCHAR(20),     `INSPECTION_COMMENTS`                           TEXT,     `INSPECTION_SCOPE`                              TEXT,     `WORK_ORDER`                                    TEXT,     `INPECTOR_NAME`                                 VARCHAR(50),     `INPECTION_COMPANY`                             VARCHAR(50),     `PHOTO`                                         INT NOT NULL AUTO_INCREMENT,      /*PRIMARY AND FOREIGN KEY DEFINITIONS*/     PRIMARY KEY (EQUIPMENT_ID, CML_ID, INSPECTION_NO),     FOREIGN KEY (EQUIPMENT_ID, CML_ID) REFERENCES CML(EQUIPMENT_ID, CML_ID),      /*ADD TABLE INDEXES TO IMPROVE PERFORMANCE*/     /*INDEX ON PHOTO FIELD REQUIRED TO ALLOW AUTO INCREMENTING OF FIELD*/     INDEX INSPECTION_INDEX (EQUIPMENT_ID, CML_ID, INSPECTION_NO),     INDEX `PHOTO` (`PHOTO`)     -- INDEX INSPECTION_DATE (INSPECTION_DATE)  ) ENGINE=InnoDB;

回答1:

回答2:

Replace all the order by ... limit 1 functionality with min/max. min/max complexity in O(n) while sort complexity is O(n*log n). You'll notice a difference for large data sets.

The LEFT JOINs are actually INNER JOINs because of conditions on the right table such as b.INTERNAL_EXTERNAL = 'INTERNAL'

INDEX CML_TYPES_INDEX (CML_TYPE) is duplication of PRIMARY KEY (CML_TYPE)

INDEX CML_INDEX (EQUIPMENT_ID, CML_ID) is duplication of PRIMARY KEY (EQUIPMENT_ID, CML_ID)

etc.

It seems to be way too much indexes in the system. For every couple of columns there is an index for (A) and for (B) and for (A,B) and for (B,A).

This usually drives the optimizer to generate bad execution plans.
You pay a lot for every DML operation (insert/update/delete)

The indexes on the small tables might damage the performance Full table scan might require less reads than traversing the index blocks.

In the following code - WHERE e.EQUIPMENT_ID like @EQUIPMENT_VARIABLE

Do you use only fixed string (no '%' and '_') like in SET @EQUIPMENT_VARIABLE = 'B1010-V001'

so the like can be actually replaced with =?

回答3:

Suggested code

I assumed the like can be replace with =.
The main key here is to retrieve only once from each source table.

SET @EQUIPMENT_VARIABLE = 'B1010-V001' ;   UPDATE      EQUIPMENT e               left join  (SELECT      min(RECOMMENDED_RBI_INTERNAL_INSPECTION_INTERVAL)  as MIN_RECOMMENDED_RBI_INTERNAL_INSPECTION_INTERVAL /*25. RECOMMENDED RBI INTERNAL INTERVAL*/                                    ,min(RECOMMENDED_RBI_EXTERNAL_INSPECTION_INTERVAL)  as MIN_RECOMMENDED_RBI_EXTERNAL_INSPECTION_INTERVAL /*28. RECOMMENDED RBI EXTERNAL INTERVAL*/                          FROM        DAMAGE_MECHANISM                           WHERE       EQUIPMENT_ID = @EQUIPMENT_VARIABLE                         ) dm              on  true              left join  (SELECT      max(case b.INTERNAL_EXTERNAL when 'INTERNAL' then a.LAST_INSPECTION_DATE end) MIN_LAST_INSPECTION_DATE_INTERNAL    /*26. LAST INSPECTION DATE INTERNAL*/                                    ,max(case b.INTERNAL_EXTERNAL when 'EXTERNAL' then a.LAST_INSPECTION_DATE end) MIN_LAST_INSPECTION_DATE_EXTERNAL    /*29. LAST INSPECTION DATE EXERNAL*/                                    ,min(END_OF_LIFE)                            as min_END_OF_LIFE                          /*31. END OF LIFE*/                                    ,GROUP_CONCAT(DISTINCT REMEDIATION_STATUS)   as GROUP_CONCAT_DISTINCT_REMEDIATION_STATUS /*XX. REMEDIATION STATUS*/                                    ,max(APPLIED_CORROSION_RATE)                 as max_APPLIED_CORROSION_RATE                                    ,min(REMAINING_LIFE_BASED_ON_ACR)            as min_REMAINING_LIFE_BASED_ON_ACR                          FROM        CML a JOIN CML_TYPES b ON a.CML_TYPE = b.CML_TYPE                          WHERE       a.EQUIPMENT_ID = @EQUIPMENT_VARIABLE AND a.STATUS NOT IN('X')                         ) ct              on  true  SET         e.MAX_COF                           = least(COF_SAFETY, COF_HEALTH, COF_ENVIRONMENT, COF_ASSETS)                                            /*24. MAX COF*/                        ,e.RECOMMENDED_RBI_INTERNAL_INTERVAL = dm.MIN_RECOMMENDED_RBI_INTERNAL_INSPECTION_INTERVAL                                                   /*25. RECOMMENDED RBI INTERNAL INTERVAL*/                    ,e.LAST_INSPECTION_DATE_INTERNAL     = ct.MIN_LAST_INSPECTION_DATE_INTERNAL                                                                  /*26. LAST INSPECTION DATE INTERNAL*/            ,e.NEXT_INSPECTION_DATE_INTERNAL     = DATE_ADD(e.LAST_INSPECTION_DATE_INTERNAL,INTERVAL FLOOR(RECOMMENDED_RBI_INTERNAL_INTERVAL*365) DAY)   /*27. NEXT INSPECTION DATE INTERNAL*/            ,e.RECOMMENDED_RBI_EXTERNAL_INTERVAL = dm.MIN_RECOMMENDED_RBI_EXTERNAL_INSPECTION_INTERVAL                                                   /*28. RECOMMENDED RBI EXTERNAL INTERVAL*/            ,e.LAST_INSPECTION_DATE_EXTERNAL     = ct.MIN_LAST_INSPECTION_DATE_EXTERNAL                                                                  /*29. LAST INSPECTION DATE EXERNAL*/            ,e.NEXT_INSPECTION_DATE_EXTERNAL     = DATE_ADD(e.LAST_INSPECTION_DATE_EXTERNAL,INTERVAL FLOOR(RECOMMENDED_RBI_EXTERNAL_INTERVAL*365) DAY)   /*30. NEXT INSPECTION DATE EXTERNAL*/              ,e.END_OF_LIFE                       = ct.min_END_OF_LIFE                                                                                    /*31. END OF LIFE*/            ,e.REMEDIATION_STATUS                = coalesce(ct.GROUP_CONCAT_DISTINCT_REMEDIATION_STATUS,'F')                                             /*XX. REMEDIATION STATUS*/            ,e.MAX_ACR                           = ct.max_APPLIED_CORROSION_RATE                                                                         /*XX. MAX ACR*/            ,e.MIN_REMAINING_LIFE                = ct.min_REMAINING_LIFE_BASED_ON_ACR                                                                    /*XX. MIN REMAINING LIFE*/  WHERE       e.EQUIPMENT_ID = @EQUIPMENT_VARIABLE ;

文章来源: MySQL - Improve UPDATE Query Performance For Complex Calculations

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