Dynamics 365 FO - Accessing the database - Microsoft Dynamics 365 Vietnam

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Dynamics 365 FO - Accessing the database

 Dynamics 365 FO - Accessing the database

Nghia Song -  Microsoft Dynamics 365 Technical Consultant

Nghia Song

Tel - WhatsApp: +84967324794

Email: songnghia.uit@gmail.com


  1. Accessing the database

  1. Content

The objectives are: 

  • Retrieve data from the database using a select statement.

  • Create, update and delete data in the database.

  • Use and build queries using kernel classes.

  • Display field: this is a field to lookup another table base on current record

  1. Select Statements Syntax

The select statement fetches or manipulates data from the database or both fetches and manipulates data from the database.


All select statements use a table variable to fetch records. This variable must be declared before a select statement can be executed.


The select statement only fetches one record, or field. To fetch additional records, you can use the next statement. The next statement fetches the next record in the table. If you use next without a preceding select command, an error occurs. Do not use next with the firstOnly find option. If you need to traverse a number of records, it is more appropriate to use a while select statement.


SelectStatement

=

select Parameters

Parameters


[ [  FindOptions  ] [  FieldList  from ] ] TableBufferVariable [ IndexClause ] [  Options  ] [  WhereClause  ] [  JoinClause  ]

FindOptions

=

crossCompany | reverse | firstFast | [ firstOnly | firstOnly10 | firstOnly100 | firstOnly1000 ] | forUpdate | noFetch | [forcePlaceholders | forceLiterals] | forceselectorder | forceNestedLoop | repeatableRead | validTimeState

FieldList

=

Field  { ,  Field  } | *

Field

=

Aggregate  (  FieldIdentifier  ) |  FieldIdentifier

Aggregate

=

sum | avg | minof | maxof | count

Options

=

[ order by , group by ,  FieldIdentifier  [ asc | desc ] { ,  FieldIdentifier  [ asc | desc ] }] | [  IndexClause  ]

IndexClause

=

index  IndexName | index hint  IndexName

WhereClause

=

where  Expression

JoinClause

=

[exists | notexists | outer ] join  Parameters


Results of a select statement are returned in a table buffer variable. If you use a field list in the select statement, only those fields are available in the table variable. If you use aggregate functions, such as sum or count, the results are returned in the fields that you perform the sum or count over. You can only count, average, or sum the integer and real fields.

Keywords used in the slect syntax

Keyword

Description

Example

asc

An option on the order by or group by clause. The sorting is ascending. (Sort is ascending by default.)

select * from custTable

    order by Name asc;

avg

Returns the average of the fields.

CustTable custTable;

;

select avg(value) from custTable;

print custTable.value;

count

Returns the number of records.

CustTable xCT;

int64 iCountRows; ;

Select COUNT(RecID) from xCT;

iCountRows = xCT.RecID;

crossCompany

Returns data for all companies that the user is authorized to read from. (A container can be added to reduce the number of companies involved.)

CustTable custTable;

container conCompanies = ['dat','dmo'];

;

select crossCompany :conCompanies

    * from custTable;

desc

An option on the order by or group by clause. The sorting is descending.

select * from custTable

    order by Name desc;

exists

A method that returns a Boolean value and a join clause.

while select AccountNum, Name from custTable

    order by AccountNum

    exists join * from ctr

    where (ctr.AccountNum ==

      custTable.AccountNum)

firstFast

A priority hint. The first row appears more quickly but the total return time for this option might be slower. The firstFast hint is automatically issued from all forms, but is rarely used directly from X++.

select firstFast custTable

    order by AccountNum;

firstOnly

Speeds up the fetch. Instructs MorphX to fetch only the first record.

static InventTable find(

    ItemId   itemId,

    boolean  update = false)

{

    InventTable inventTable;

    ;

    inventTable.selectForUpdate

        (update);

    if (itemId)

    {

         select firstonly inventTable

            index hint ItemIdx

            where inventTable.itemId

                == itemId;

    }

    return inventTable;

}

firstOnly10

Same as firstOnly, except returns 10 rows instead of one.


firstOnly100

Same as firstOnly, except returns 100 rows instead of one.


firstOnly1000

Same as firstOnly, except returns 1000 rows instead of one.


forceLiterals

> [!note] >

You are advised not to use the forceLiterals keyword in X++ select statements, because it could expose code to an SQL injection security threat.

forceLiterals instructs the kernel to reveal the actual values that are used in where clauses to the Microsoft SQL Server database at the time of optimization.

forceLiterals and forcePlaceholders are mutually exclusive.


forceNestedLoop

Forces the Microsoft SQL Server database to use a nested-loop algorithm to process a particular SQL statement containing a join algorithm. This means that a record from the first table is fetched before any records from the second table are fetched. Typically, other join algorithms, such as hash-joins and merge-joins, would be considered. This keyword is often combined with the forceSelectOrder keyword.

while select forceSelectOrder

    forceNestedLoop inventTransThis

    index hint TransIdIdx

    where inventTransThis.InventTransId

        == inventTrans.InventTransId

        && inventTransThis.StatusIssue

        <= StatusIssue::ReservOrdered

forcePlaceholders

Instructs the kernel not to reveal the actual values used in where clauses to the SQL Server database at the time of optimization. This is the default in all statements that are not join statements.

The advantage of using this keyword is that the kernel can reuse the access plan for other similar statements with other search values. The disadvantage is that the access plan is computed without taking into consideration that data distribution might not be even. The access plan is an on-average access plan.

forcePlaceholders and forceLiterals are mutually exclusive.

static void forcePlaceHoldersExample(Args _args)

{

    SalesTable salesTable;

    SalesLine salesLine;

    ;

    while select forcePlaceholders salesLine

        join salesTable

           where salesTable.SalesId ==

            salesLine.SalesId

               && salesTable.SalesId == '10'

    {

        //more code

    }

}

forceSelectOrder

Forces the SQL Server database to access the tables in a join in the specified order. If two tables are joined, the first table in the statement is always accessed first. This keyword is often combined with the forceNestedLoop keyword.

display ForecastHasPurch hasForecastPurch()

{

    ForecastPurch   forecastPurch;

    InventDim       inventDim;

    ;

    select firstOnly forcePlaceholders

        forceSelectOrder recId

        from forecastPurch

        index hint ItemIdx

        where forecastPurch.itemId == this.itemId

    exists join inventDim

        index hint DimIdIdx

        where inventDim.inventDimId ==

            forecastPurch.inventDimId

        && inventDim.configId == this.configId;

    return forecastPurch.recId;

}

forUpdate

Selects records exclusively for update. Depending on the underlying database, the records may be locked for other users.

ttsBegin;

while select forUpdate ledgerJournalTrans

    index hint NumVoucherIdx

    where ledgerJournalTrans.journalNum ==

    _journalNum &&

    ledgerJournalTrans.voucher == _voucher

{

    ledgerJournalTrans.doDelete();

    counter++;

}

if (counter

    && ledgerJournalTable.journalType

    != LedgerJournalType::Periodic)

{

    NumberSeq::release(

      ledgerJournalTable.voucherSeries,

      _voucher);

}

ttsCommit;

group by

Instructs the database to group selected records by fields.

CustTable custTable;

;

while select sum(CreditMax) from custTable

    group by CustGroup

{

    print custTable.CustGroup, " ",custTable.CreditMax;

}

index

Instructs the database to sort the selected records as defined by the index.

CustTable custTable;

;

while select AccountNum, Name from custTable

    index AccountIdx

{

    print custTable.AccountNum, " ", custTable.Name;

}

index hint

Gives the database a hint to use this index to sort the selected records as defined by the index. The database can ignore the hint.

 Note

A wrong index hint can have a big performance impact. Index hints should only be applied to SQL statements that do not have dynamic where clauses or order by clauses, and where the effect of the hint can be verified.

while select forUpdate ledgerJournalTrans

    index hint NumVoucherIdx

    where ledgerJournalTrans.journalNum

        == _journalNum

join

Used to join tables on a column that is common to both tables. The join criteria are specified in the where clause because there is no on keyword in X++ SQL.

Reduces the number of SQL statements that are needed if you want to loop through a table and update transactions in a related table.

For example, if you process 500 records in a table, and want to update related records in another table, and use a nested while select to do this, there will be 501 trips to the database. If you use a join, there will be a single trip to the database.

while select ledgerTable

    join ledgerTrans

        where ledgerTrans.accountNum ==

            ledgerTable.accountNum

    {

        amountMST += ledgerTrans.amountMST;

    }

maxof

Returns the maximum of the fields.

CustTable custTable;

;

select maxof(CreditMax) from custTable;

minof

Returns the minimum of the fields.

CustTable custTable;

;

select minof(CreditMax) from custTable;

noFetch

Indicates that no records are to be fetched at present. This is typically used when the result of the select is passed on to another application object, for example, a query that performs the actual fetch.

select noFetch custTable

    order by AccountNum

notExists

Chosen only if there are no posts.

while select AccountNum, Name from custTable

    order by AccountNum

    notExists join * from ctr

    where (ctr.AccountNum ==

        custTable.AccountNum)

optimisticLock

Forces a statement to run with Optimistic Concurrency Control even if a different value is set on the table.

For more information, see .

select optimisticLock custTable

    where custTable.AccountNum > '1000'

order by

Instructs the database to sort the selected records by fields in the order by list.

select * from custTable

    order by accountNum desc

    where custTable.AccountNum > "100";

outer

Returns all rows from the first-named table, including rows that have no match in the second-named table. This is a left outer join, although there is no left keyword. There is no right outer join in X++ SQL.

X++Copy

while select AccountNum

 from custTable

 order by AccountNum

 outer join * from custBankAccount

 where custBankAccount.AccountNum ==

    custTable.AccountNum

{

 print custTable.AccountNum,

    custBankAccount.DlvMode;

}

pause;

pessimisticLock

Forces a statement to run with Pessimistic Concurrency Control even if a different value is set on the table.

For more information, see Optimistic Concurrency Control.

select pessimisticLock custTable

    where custTable.AccountNum > '1000';

repeatableRead

Specifies that no other transactions can modify data that has been read by logic inside the current transaction, until after the current transaction completes.

An explicit transaction completes at either ttsAbort or at the outermost ttsCommit.

For a stand-alone select statement, the transaction duration is the duration of the select command. However, the database sometimes enforces the equivalent of repeatableRead in individual select statements even without this keyword appearing in your X++ code (depending on how the database decides to scan the tables).

For more information, see the documentation for the underlying relational database product.

reverse

Records are returned in reverse order.

select reverse custTable

    order by AccountNum;

sum

Returns the sum of the fields. Can be used to sum all accounts, order lines, and so on.

CustTable custTable;

;

select sum(CreditMax) from custTable;

validTimeState

Filters rows from a table that has its ValidTimeStateFieldType property set to a value other than None. For more information, see Valid Time State Tables and Date Effective Data.

static void VtsJob1(Args _args)

{

    // A VTS table in AX 2012.

    CustPackingSlipTransHistory xrec1;

    utcDateTime myDateFrom , myDateTo;

    anytype myAnytype = -1;

    myDateFrom = DateTimeUtil::utcNow();

    myDateTo = myDateFrom;

    SELECT 

        validTimeState(myDateFrom, myDateTo)

        FROM xrec1;

    myAnytype = xrec1.getFieldValue(&quot;RecId&quot;);

    info(myAnytype);

}

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