SQL Server conversion error while using INSERT

Question

I have an existing table full of data that can be created using

CREATE TABLE __EpisodeCost
(
    ActivityRecordID INT NOT NULL, 
    ActCstID NVARCHAR(15), 
    VolAmt FLOAT, 
    ActCnt FLOAT, 
    TotCst FLOAT, 
    ResCstID NVARCHAR(50)
);

This comes from a feed that I have no control over, and I want to convert it to my own version called EpisodeCost

CREATE TABLE EpisodeCostCtp
(
    ActivityRecordID INT NOT NULL, 
    ActCstID NVARCHAR(6), 
    ResCstID NVARCHAR(7), 
    ActCnt NVARCHAR(7), 
    TotCst DECIMAL(18, 8) 
);

Now I have a problem with conversions. I can fulfill the request

SELECT 
    ActivityRecordID, 
    Cast(ActCstID AS NVARCHAR(6)), 
    Cast(ResCstID AS NVARCHAR(7)), 
    Cast(LTRIM(STR(ActCnt, 10)) AS NVARCHAR(7)), 
    Cast(TotCst AS DECIMAL(18, 8)) 
FROM __EpisodeCostCtp;

and it provides data, however, when I try to execute

INSERT INTO EpisodeCostCtp 
    (
        ActivityRecordID, 
        ActCstID, 
        ResCstID, 
        ActCnt, 
        TotCst 
    ) 
SELECT 
    ActivityRecordID, 
    Cast(ActCstID AS NVARCHAR(6)), 
    Cast(ResCstID AS NVARCHAR(7)), 
    Cast(LTRIM(STR(ActCnt, 10)) AS NVARCHAR(7)), 
    Cast(TotCst AS DECIMAL(18, 8)) 
FROM __EpisodeCostCtp;

I get

Msg 8115, Level 16, State 8, Line 102 An arithmetic overflow error converting numeric data to numeric data. Application completed.

Why can I SELECTuse the appropriate roles but cannot INSERTin the target table?

---

Change I still don’t know what is going on here.

Following Serg's recommendations, I tried to find the problematic entries, but the query

SELECT 
    ActivityRecordID, 
    Cast(ActCstID AS NVARCHAR(6)), 
    Cast(ResCstID AS NVARCHAR(7)), 
    Cast(LTRIM(STR(ActCnt, 10)) AS NVARCHAR(7)), 
    Cast(TotCst AS DECIMAL(18, 8))      
FROM __EpisodeCostCtp
WHERE TotCst > 9.999999999999999e9;

. 9.999999999999999e8 , / . scince INSERT DECIMAL(36, 18), , . , , SELECT , INSERT , .

Answer 1

,

SET ARITHABORT OFF

from https://docs.microsoft.com/en-us/sql/t-sql/statements/insert-transact-sql

INSERT (, ), , Database Engine , SET ARITHABORT ON. , . , SET ARITHABORT SET ANSI_WARNINGS OFF, INSERT, DELETE UPDATE , , , SQL Server NULL. NULL, , .

Answer 2

, TotCst DECIMAL (18,8). 2008 SQL SERVER , . , .

SQL SERVER 2012:

 DECLARE @float FLOAT 
 SET @float = 12345678911.12
 SELECT CAST(@float AS decimal(18,8))

: float .

DECIMAL (19,8):

 DECLARE @float FLOAT 
 SET @float = 12345678911.12
 SELECT CAST(@float AS decimal(19,8))

: 12345678911.12000100

EDIT: , . , , , , DECIMAL (18.8)

Answer 3

, ,

SELECT *       
FROM __EpisodeCostCtp
WHERE TotCst > 9.999999999999999e9;