Question

从SQL Server切换到Oracle。如何将字符串连接到循环内的变量？在SQL Server中，我会编写类似

的内容

DECLARE @var varchar(max);
WHILE ([I'm doing something or whatever on a table])
BEGIN
    SET @var = @var + ' additional text';
END
SELECT @var AS 'result';

到目前为止，这是我在Oracle中的存储过程。（将其演变为NHibernate的ClassMap文件的autogen）

CREATE OR REPLACE PROCEDURE WWNA.UT_MAPPINGHELPER
(
    TABLE_NAME IN ALL_TABLES.TABLE_NAME%TYPE
    , OWNER_NAME IN ALL_TABLES.OWNER%TYPE
    , CLASS_DEFINITION IN OUT VARCHAR2
)
   IS
   CURSOR TABLE_INFO_CUR
   IS
    SELECT 
        T.TABLE_NAME
        , C.COLUMN_NAME
        ,C.DATA_TYPE
        ,C.DATA_LENGTH
        ,C.DATA_PRECISION
        ,C.NULLABLE
    FROM 
        ALL_TABLES T
        JOIN
        ALL_TAB_COLUMNS C
            ON T.TABLE_NAME = C.TABLE_NAME
                AND T.OWNER = C.OWNER
    WHERE
        T.TABLE_NAME = :TABLE_NAME
        AND T.OWNER = :OWNER_NAME;
    TABLE_INFO_ROW TABLE_INFO_CUR%ROWTYPE;
    build_sql varchar2;
BEGIN
    --VARIABLE build_sql varchar2(4000);
    :build_sql := '';
    OPEN TABLE_INFO_CUR;

    LOOP
        FETCH TABLE_INFO_CUR INTO TABLE_INFO_ROW;
        EXIT WHEN TABLE_INFO_CUR%NOTFOUND;
        SELECT (:build_sql || ' ' || TABLE_INFO_ROW.TABLE_NAME || ' ' || TABLE_INFO_ROW.COLUMN_NAME || ' ' || TABLE_INFO_ROW.DATA_TYPE) INTO :build_sql;
    END LOOP;
    :CLASS_DEFINITION := :build_sql;  

    --DBMS_OUTPUT.put_line (CLASS_DEFINITION);


END;

由于

Answer 1

CREATE OR REPLACE PROCEDURE WWNA.UT_MAPPINGHELPER
(
    TABLE_NAME IN ALL_TABLES.TABLE_NAME%TYPE
    , OWNER_NAME IN ALL_TABLES.OWNER%TYPE
    , CLASS_DEFINITION IN OUT VARCHAR2
)
   IS
   CURSOR TABLE_INFO_CUR
   IS
    SELECT 
        T.TABLE_NAME
        , C.COLUMN_NAME
        ,C.DATA_TYPE
        ,C.DATA_LENGTH
        ,C.DATA_PRECISION
        ,C.NULLABLE
    FROM 
        ALL_TABLES T
        JOIN
        ALL_TAB_COLUMNS C
            ON T.TABLE_NAME = C.TABLE_NAME
                AND T.OWNER = C.OWNER
    WHERE
        T.TABLE_NAME = :TABLE_NAME
        AND T.OWNER = :OWNER_NAME;

    build_sql varchar2(32767);
BEGIN
    --build_sql := ''; --Not needed, build_sql is already initialised to NULL


    FOR cur_rec IN TABLE_INFO_CUR
    LOOP
        build_sql := build_sql || ' ' || 
                     cur_rec.TABLE_NAME || ' ' || 
                     cur_rec.COLUMN_NAME || ' ' || 
                     cur_rec.DATA_TYPE;
    END LOOP;
    CLASS_DEFINITION := build_sql;  

    --DBMS_OUTPUT.put_line (CLASS_DEFINITION);


END;

您需要定义变量CLASS_DEFINITION。

使用CURSOR FOR LOOP可以为您打开和关闭光标以及批量提取结果。

您也可以使用CONCAT功能代替||功能。

Answer 2

如果要在过程中使用build_sql值执行此操作，请忽略前导冒号。这是一个典型值，这里不适用。

同时在顶部声明build_sql变量的长度。这有点令人困惑，因为你可以省去参数的长度，但你需要为声明的变量做长度。

这是你的过程的一个切碎版本，显示build_sql操纵。另请注意，CLASS_DEFINITION参数变量不应具有冒号前缀：

CREATE OR REPLACE PROCEDURE WWNA.UT_MAPPINGHELPER
(
    TABLE_NAME IN ALL_TABLES.TABLE_NAME%TYPE
    , OWNER_NAME IN ALL_TABLES.OWNER%TYPE
    , CLASS_DEFINITION IN OUT VARCHAR2
)
IS
   ...
   build_sql varchar2(4000);
BEGIN
   build_sql := '';
   ...
   LOOP
      build_sql := build_sql || 'whatever';
   END LOOP;
   CLASS_DEFINITION := build_sql;  
END;

另请注意，您不需要build_sql := ''行 - 变量值将默认为空白。或者，您可以在声明时指定初始值：

CREATE OR REPLACE PROCEDURE WWNA.UT_MAPPINGHELPER
(
    TABLE_NAME IN ALL_TABLES.TABLE_NAME%TYPE
    , OWNER_NAME IN ALL_TABLES.OWNER%TYPE
    , CLASS_DEFINITION IN OUT VARCHAR2
)
IS
   ...
   build_sql varchar2(4000) := 'start of my sql';
BEGIN
   ...

Oracle相当于T-SQL SET @var = @var +'';

2 个答案: