Help Center/ GaussDB(DWS)/ Tool Guide/ DSC: SQL Syntax Migration Tool/ Oracle Syntax Migration/ System Functions/ String Functions
Updated on 2023-04-03 GMT+08:00
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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.

The REPLACE function in Oracle contains two mandatory parameters and one optional parameter. The REPLACE function in GaussDB(DWS) contains 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
Parent topic: System Functions