Help Center/ GaussDB(DWS)/ Tool Guide/ DSC/ Oracle Syntax Migration/ DML
Updated on 2024-12-09 GMT+08:00
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DML

This section describes the migration syntax of Oracle DML. The migration syntax decides how the keywords/features are migrated.

For details, see the following topics:

SELECT

INSERT

MERGE

SELECT

Overview

The Oracle SELECT statement starts a query, with an optional ORDER BY clause. The clause is used to retrieve records from one or more tables in a database.

Input - SELECT

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SELECT col1, col2
  FROM tab1;

Output

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SELECT col1, col2
  FROM tab1;
  1. Order of Clauses

    The HAVING clause must follow the GROUP BY clause. However, Oracle allows HAVING to be in front of or behind the GROUP BY clause. In the target database, the HAVING clause is moved to behind the GROUP BY clause.

    Figure 1 Input - Order of Clauses
    Figure 2 Output - Order of Clauses
  2. Extended Group By Clause

    The GROUP BY clause can be specified if you want the database to group the selected rows based on the value of expr(s). If this clause contains CUBE, ROLLUP, or GROUPING SETS extensions, then the database produces super-aggregate groupings in addition to the regular groupings. These features are not supported by GaussDB(DWS) but can be enabled using the UNION ALL operator.

    Figure 3 Input - Extended group by clause
    Figure 4 Output - Extended group by clause

    GROUPING_ID and ROLLUP

    GROUPING_ID returns a number that corresponds to the GROUPING bit vector associated with a row. GROUPING_ID is applicable only in a SELECT statement containing a GROUP BY extension, such as the ROLLUP operator and GROUPING function. In queries with multiple GROUP BY expressions, determining the GROUP BY level of a particular row requires multiple GROUPING functions, which may complicate SQL statements. In such scenarios, GROUPING_ID is used to avoid statement complexity.

  3. Table Name Inside Brackets

    Table names do not need to be specified within parentheses. However, allows using brackets.

    Figure 5 Input - Table name inside brackets
    Figure 6 Output - Table name inside brackets
  4. UNIQUE Keyword

    Unique keyword is migrated as Distinct keyword.

    Input - SELECT UNIQUE

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    SELECT UNIQUE a.item_id id,
                     a.menu_id parent_id,a.serialno menu_order
                FROM ctp_menu_item_rel a WHERE  
    a.item_id IN(SELECT UNIQUE id FROM ctp_temp_item_table);

    Output

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    SELECT DISTINCT a.item_id id,
   a.menu_id parent_id,a.serialno menu_order
     FROM ctp_menu_item_rel a WHERE  
       a.item_id IN(SELECT UNIQUE id FROM ctp_temp_item_table);
  5. USERENY

    Input - CLIENT_INFO

    Returns user session information.

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    SELECT 1
FROM   sp_ht ht
WHERE  ht.hth = pi_contract_number
       /*  AND ht.contract_status = 2  --delete by leinian 2014-03-03(ECO)  */
       AND ht.contract_status IN ( 1, 2 ) /*  add by leinian 2014-03-20(ECO)  */
       AND Nvl(ht.s3_pilot_flag, 'N') = 'N'
       AND NOT EXISTS (SELECT 1
                       FROM   asms.asms_lookup_values alv
                       WHERE  alv.type_code = 'HTLX_LOAN'
                              AND ht.htlx = alv.code)
       AND ht.duty_erp_ou_id = To_number(Nvl(Rtrim(Ltrim(Substr(Userenv(
                                                         'client_info'),
                                                         1,
                                                         8))), 218))
       AND ht.source_code = 'ECONTRACT'
       AND ht.needing_engineering_service IS NOT NULL
       AND ht.khm != '28060'
       AND ht.htlx != '111' ;

    Output

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    SELECT
          1
     FROM
          sp_ht ht
     WHERE
          ht.hth = pi_contract_number /*   AND ht.contract_status = 2  --delete by leinian 2014-03-03(ECO)   */
          AND ht.contract_status IN (
               1
               ,2
          ) /*   add by leinian 2014-03-20(ECO)   */
          AND Nvl( ht.s3_pilot_flag ,'N' ) = 'N'
          AND NOT EXISTS (
               SELECT
                         1
                    FROM
                         asms.asms_lookup_values alv
                    WHERE
                         alv.type_code = 'HTLX_LOAN'
                         AND ht.htlx = alv.code
          )
          AND ht.duty_erp_ou_id = To_number( Nvl( Rtrim( Ltrim( SUBSTR( MIG_ORA_EXT.USERENV ( 'client_info' ) ,1 ,8 ) ) ) ,218 ) )
          AND ht.source_code = 'ECONTRACT'
          AND ht.needing_engineering_service IS NOT NULL
          AND ht.khm != '28060'
          AND ht.htlx != '111' ;

    USERENV('CLIENT_INFO)

    After the function in the package is converted, the function tag is not deleted. The svproduct_is_for_pa function in 4_sad_lookup_contract_pkg.bdy is used.

    USERENV('CLIENT_INFO')

    USERENV used during the migration process. Migration fails due to the tool.

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    SELECT 1
FROM   sp_ht ht
WHERE  ht.hth = pi_contract_number
/*  AND ht.contract_status = 2  --delete by leinian 2014-03-03(ECO)  */
AND ht.contract_status IN ( 1, 2 ) /*  add by leinian 2014-03-20(ECO)  */
AND Nvl(ht.s3_pilot_flag, 'N') = 'N'
/*  add by yangyirui 2012-09-10: S3 Data is not provided for the contract cutover.  */
AND NOT EXISTS (SELECT 1
FROM   asms.asms_lookup_values alv
WHERE  alv.type_code = 'HTLX_LOAN'
AND ht.htlx = alv.code)
AND ht.duty_erp_ou_id = To_number(Nvl(Rtrim(Ltrim(Substr(Userenv(
'client_info'),
1,
8))), 218))
AND ht.source_code = 'ECONTRACT'
AND ht.needing_engineering_service IS NOT NULL
AND ht.khm != '28060'
AND ht.htlx != '111'

    Input

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    Error message :client_info argument for USERENV function is not supported by the DSC.

4_sad_lookup_contract_pkg

================================
CREATE OR REPLACE PACKAGE BODY SAD.sad_lookup_contract_pkg IS
 FUNCTION svproduct_is_for_pa(pi_contract_number IN VARCHAR2) RETURN VARCHAR2 IS
    l_flag VARCHAR2(1) := 'N';
  BEGIN
    FOR rec_lookup IN (SELECT 1
       FROM asms.asms_lookup_values alv
      WHERE alv.type_code = 'HTLX_LOAN'
        AND alv.duty_erp_ou_id = to_number(nvl(rtrim(ltrim(substr(userenv('client_info'), 1, 8))), 218))
                      )
    LOOP
      l_flag := 'Y';
    END LOOP;

    RETURN l_flag;
  END svproduct_is_for_pa;
END sad_lookup_contract_pkg;
/

    Output

    CREATE OR replace FUNCTION sad_lookup_contract_pkg.Svproduct_is_for_pa ( 
pi_contract_number IN VARCHAR2) 
RETURN VARCHAR2 
IS 
  l_flag VARCHAR2 ( 1 ) := 'N'; 
BEGIN 
    FOR rec_lookup IN (SELECT 1 
                       FROM   asms.asms_lookup_values alv 
                       WHERE  alv.type_code = 'HTLX_LOAN' 
                              AND alv.duty_erp_ou_id = To_number(Nvl( 
                                                       Rtrim(Ltrim(Substr( 
                                  mig_ora_ext.Userenv ( 
                                  'client_info'), 1, 8)) 
                                                       ), 
                                                                            218) 
                                                       )) 
    LOOP 
        l_flag := 'Y'; 
    END LOOP; 

    RETURN l_flag; 
END; 

/

INSERT

Overview

The Oracle INSERT statement is used to insert a single record or multiple records into a table.

NOLOGGING

NOLOGGING is commented from the inserted script.

Oracle Syntax

Syntax After Migration

 
INSERT INTO TBL_ORACLE NOLOGGING
  SELECT emp_id, emp_name
   FROM emp;
 
INSERT INTO TBL_ORACLE /*NOLOGGING*/
  SELECT emp_id, emp_name
   FROM emp;
  1. INSERT ALL

    The Oracle INSERT ALL statement is used to add multiple rows using a single INSERT statement. The rows can be inserted into either a single table or multiple tables. The target query is converted as a common table expression (CTE).

    Figure 7 Input - INSERT ALL
    Figure 8 Output - Insert All
  2. INSERT FIRST

    The Oracle INSERT FIRST is used to execute an INSERT statement when the first condition is true; other statements are ignored. The target query is converted as a CTE.

    Figure 9 Input - Insert first
    Figure 10 Output - Insert first
  3. INSERT with Table Alias
    The Oracle table aliases are used to clarify and improve readability when referring to a table in a query by assigning it a name or code. INSERT with table alias can be used with INSERT INTO statement. The tool supports the migration of INSERT INTO statements with table alias.
    1. Blogic Operations

      Input - INSERT with Table Alias

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      CREATE
     OR REPLACE FUNCTION myfct RETURN VARCHAR2 IS res VARCHAR2 ( 200 ) ;
     BEGIN
          res := 100 ;
          INSERT INTO emp18 RW ( RW.empno ,RW.ename ) SELECT
               res ,RWN.ename
          FROM
               emp16 RWN ;
               COMMIT ;
          RETURN res ;
END ;
/

      Output

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      CREATE
     OR REPLACE FUNCTION myfct RETURN VARCHAR2 IS res VARCHAR2 ( 200 ) ;
     BEGIN
          res := 100 ;
          INSERT INTO emp18 ( empno ,ename ) SELECT
               res ,RWN.ename
          FROM
               emp16 RWN ;
               /* COMMIT ; */
          null ;
          RETURN res ;
END ;
/
    2. Bulk Operations

      Input - INSERT with Table Alias

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      INSERT
     INTO
          Public.emp14 ats (
               ats.empno
               ,ats.ename
          )
     VALUES (
          3
          ,'Categories'
     )
;

      Output

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      INSERT
     INTO
          Public.emp14 (
               empno
               ,ename
          ) SELECT
                    3
                    ,'Categories'
;

      Input - INSERT with Table Alias

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      INSERT
     INTO
          "abc" . "emp18" wmc (
               wmc.empno
               ,wmc.ename
          ) SELECT
                    wmc.empno
                    ,wm_concat (wmc.ename) AS eName
               FROM
                    emp16 wmc
               GROUP BY
                    empno
;

      Output

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      INSERT
     INTO
          "abc" . "emp18" (
               empno
               ,ename
          ) SELECT
                    wmc.empno
                    ,STRING_AGG (
                         wmc.ename
                         ,','
                    ) AS eName
               FROM
                    emp16 wmc
               GROUP BY
                    empno
;

      Input - INSERT with Table Alias

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      INSERT
     INTO
          emp14 "TABLE" (
               "TABLE" .empno
               ,ename
          ) SELECT
                    empno
                    ,ename
               FROM
                    emp12
               WHERE
                    emp12.salary > (
                         SELECT
                                   MAX( salary )
                              FROM
                                   emp13 "TABLE"
                              WHERE
                                   "TABLE" .empno > 5
                    )
;

      Output

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      INSERT
     INTO
          emp14 (
               empno
               ,ename
          ) SELECT
                    empno
                    ,ename
               FROM
                    emp12
               WHERE
                    emp12.salary > (
                         SELECT
                                   MAX( salary )
                              FROM
                                   emp13 "TABLE"
                              WHERE
                                   "TABLE" .empno > 5
                    )
;

MERGE

MERGE is an ANSI-compliant SQL syntax operator used to select rows from one or more sources for updating or inserting a table or view. The criteria for updating or inserting the target table or view can be specified.

DSC uses multiple methods to migrate MERGE to SQL statements compatible with GaussDB(DWS).

Configure parameter mergeImplementation as follows:

  • Set to With by default. In this option, the target query is converted as a CTE.
Figure 11 Input - MERGE
Figure 12 Output - MERGE
  • Set to SPLIT. In this option, the MERGE statement is split into multiple INSERT and UPDATE statements.
Figure 13 Input - MERGE
Figure 14 Output - MERGE
Parent topic: Oracle Syntax Migration