如何在sql select语句中创建列并设置默认值

Question

我正在尝试为已经派生的列"Sub1"设置默认文本值这可能吗？我已经使用值0为要派生的列创建了占位符.如果它很重要,我正在Teradata中工作.....谢谢!

select c_clm
,dt.Claimant_Name
,dt.i_ssn
,0 as "Time_Period"
,0 as "Unit_ID",
/*,idv.C_PDT AS "Product"
,er.C_FRM_POL AS "Group Product",*/
(case
 when idv.c_pdt is null then 'GLTC' 
 else idv.c_pdt
 end) as "Product_ID"
,c_ams_clm as "DBS_UserID"
,upc_indiv_org_id as "DBS_EEID"
,0 as "Categ"
,0 as Categ_sort
,0 as "Sub1"
,0 as "Sub1_Sort"
,0 as "Sub2"
,0 as "Sub2_Sort"
,0 as "MTD_Num" 
,0 as "MTD_Denom"
,dt.i_pol as "Policy_Number"
,COALESCE (erpol.n_pol,idv.n_pol, ks.n_pol) 

Answer 1

你想这样做:

select '0' as Sub1

您可以直接指定文本值,方法与数字相同.

或者,您是否尝试在SELECT中为NULL时为列分配值.为此,请使用COALESCE:

select coalesce(Sub1, '0') as Sub1

Answer 2

如果您询问如何使用字符串常量填充列，只需放入单引号并为其命名。通常最好还指定所需的列类型。例如：

select 'Text String' (VARCHAR(255)) as sub1

请注意，如果您使用双引号，Teradata 会认为您引用的是该名称的列（因此您会收到错误消息。