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String Functions

This section describes the following string functions

LISTAGG

LISTAGG is used to order data in columns within each group specified in the ORDER BY clause and concatenates the order results.

Figure 1 Input - Listagg
Figure 2 Output - Listagg

LISTAGG can be migrated after MigSupportForListAgg is set to false.

Input- LISTAGG

SELECT LISTAGG(BRANCH_ID, ',') WITHIN GROUP(ORDER BY AREA_ORDER) PRODUCTRANGE
                       FROM (SELECT DISTINCT VB.BRANCH_ID,
                                             VB.VER_ID,
                                             VB.AREA_ORDER
                               FROM SPMS_VERSION_BRANCH VB, SPMS_NODE_SET NS
                              WHERE VB.BRANCH_TYPE IN ('1', '3')
                                AND VB.AGENCY_BRANCH = NS.BRANCH_ID);

Output

SELECT LISTAGG (BRANCH_ID,',') WITHIN GROUP (
 ORDER BY AREA_ORDER ) PRODUCTRANGE
 FROM ( SELECT
         DISTINCT VB.BRANCH_ID
         ,VB.VER_ID
         ,VB.AREA_ORDER
          FROM
          SPMS_VERSION_BRANCH VB
         ,SPMS_NODE_SET NS
          WHERE VB.BRANCH_TYPE IN (
           '1','3')
         AND VB.AGENCY_BRANCH = NS.BRANCH_ID)
;

STRAGG

STRAGG is a string aggregate function used to collect values from multiple rows into a comma-separated string.

Input-STRAGG

SELECT DEPTNO,ENAME,STRAGG(ename) over (partition by deptno order by
           ename RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) 
                AS ENAME_STR FROM EMP;

Output

SELECT DEPTNO,ENAME,STRING_AGG (
    ename,',') over( partition BY deptno ORDER BY 
 ename RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED 
 FOLLOWING ) AS ENAME_STR
    FROM EMP
;

WM_CONCAT

WM_CONCAT is used to aggregate data from a number of rows into a single row, giving a list of data associated with a specific value.

Figure 3 Input - WM_Concat
Figure 4 Output - WM_Concat

NVL2 and REPLACE

NVL2( expression, value1, value2) is a function used to determine the value returned by a query based on whether a specified expression is null or not. If the expression is not null, then NVL2 returns value1. If the expression is null, then NVL2 returns value2.

Input - NVL2

NVL2(Expr1, Expr2, Expr3)

Output

DECODE(Expr1, NULL, Expr3, Expr2)

The REPLACE function is used to return char with every occurrence of search_string replaced with replacement_string. If replacement_string is omitted or null, then all occurrences of search_string are removed.

In Oracle, the REPLACE function requires two mandatory parameters and one optional parameter. The REPLACE function in GaussDB(DWS) requires three mandatory parameters.

Input - Nested REPLACE

CREATE
     OR REPLACE FUNCTION F_REPLACE_COMMA ( IS_STR IN VARCHAR2 ) RETURN VARCHAR2 IS BEGIN
               IF
                         IS_STR IS NULL
                         THEN RETURN NULL ;
                    ELSE
                    RETURN REPLACE( REPLACE( IS_STR ,'a' ) ,CHR ( 10 ) ) ;
          END IF ;
END F_REPLACE_COMMA ;
/

Output

CREATE
     OR REPLACE FUNCTION F_REPLACE_COMMA ( IS_STR IN VARCHAR2 ) RETURN VARCHAR2 IS BEGIN
               IF
                         IS_STR IS NULL
                         THEN RETURN NULL ;
                    ELSE
                    RETURN REPLACE( REPLACE( IS_STR ,'a' ,'' ) ,CHR ( 10 ) ,'' ) ;
          END IF ;
end ;
/

Input - More than one REPLACE

SELECT
          REPLACE( 'JACK and JUE' ,'J', '' ) "Changes"
          ,REPLACE( 'JACK1 and JUE' ,'J' ) "Changes1"
          ,REPLACE( 'JACK2 and JUE' ,'J' ) "Changes2"
     FROM
          DUAL
;

Output

SELECT
          REPLACE( 'JACK and JUE' ,'J' ,'' ) "Changes"
          ,REPLACE( 'JACK1 and JUE' ,'J' ,'' ) "Changes1"
          ,REPLACE( 'JACK2 and JUE' ,'J' ,'' ) "Changes2"
     FROM
          DUAL
;

Input - REPLACE with Three parameters

SELECT
          REPLACE( '123tech123' ,'123', '1')
     FROM
          dual
;

Output

SELECT
          REPLACE( '123tech123' ,'123' , '1' )
     FROM
          dual
;

QUOTE

QUOTE allows the user to embed single-quotes in literal strings without having to resort to double quotes. That is, you can use single quotes to specify a literal string.

For example:

SELECT q'[I'm using quote operator in SQL statement]' "Quote (q) Operator" FROM dual;
Figure 5 Input - Quote
Figure 6 Output - Quote