Insert NULL values into INT & STRING columns - sql

Question

I need to insert null values ​​in integer and string columns but in the data set that it obtains before obtaining values ​​"---" for the case of string and "NA" for the case of INT, necessary when you have those values ​​are inserted as void I'm using SQL Sever and my query is like that.
INSERT INTO BOEMIC01
(MICRO_DATE, MICRO_YEAR, MICRO_MONTH, MICRO_WEEK, MICRO_DIVISION, MICRO_SUBDIVISION, MICRO_CODE_COUNTRY, MICRO_COUNTRY, MICRO_CODE_CENTER, MICRO_CENTER, MICRO_FREQ, MICRO_TOTAL_M, MICRO_TOTAL_Y, MICRO_TOTAL_Z, MICRO_ID_PROCESS, MICRO_DESC_PROCESS, MICRO_TOTAL_A, MICRO_TOTAL_B, MICRO_TOTAL_C, MICRO_ID_POINT, MICRO_DESC_POINT, MICRO_CODE_MATERIAL, MICRO_DESC_MATERIAL, MICRO_TOTAL_D, MICRO_TOTAL_E, MICRO_TOTAL_F) VALUES
(
'2019-01-15',
'2019',
'1',
'3',
'X',
'Y',
'P001',
'USA',
'USA1',
'USA2',
'Daily',
'2',
'2',
'0',
'158',
'Enva',
'2',
'2',
'0',
'344',
'2',
'---', --NULL
'---', --NULL
'NA', --NULL
'NA', --NULL
'NA' --NULL
)

Answer 1

To insert NULL values use the NULL keyword. As in:
insert into t (col)
values (null);
To insert the default value, which is usually null, just leave the column out of the column list entirely:
insert into t (col1)
values ('happy value');
col2 will be set to its default value -- which is NULL if no other default is defined.
If you are inserting values from another source, then use try_convert() or nullif() For example:
insert into t (col_str, col_int)
values (nullif(#col_str, '---'), try_convert(int, #col_int));

Answer 2

Also, as a matter of standard practice, you should always use query parameters to supply any literal values to your queries, to avoid "SQL injection" issues. For instance, your query would now read:
INSERT INTO BOEMIC01
(MICRO_DATE, MICRO_YEAR, MICRO_MONTH, [...])
VALUES(?, ?, ? [...])
Notice the ? symbols and notice also that they are not in quotes.
Then, when you execute the query, you supply both the SQL string and, separately, an array of values that are to be substituted for each ? in order of occurrence. Now, SQL cannot misinterpret any value as "part of the SQL," because it isn't. Different sets of parameter values can be supplied to the same SQL string each time.
You can use functions such as NULLIF() as mentioned in BJones' comment: NULLIF('---', ?) ... the parameter's value will be passed to the NULLIF function as its second argument. I think that's a fine way to handle your requirement (and it should have been offered as "an answer").

Answer 3

It really depends where the values are coming from, but if for example this insert is inside a Stored Procedure and the values are coming in via parameters then the following shows how to ensure null values for the cases specified. (Irrelevant columns left out for brevity):
INSERT INTO BOEMIC01 (... MICRO_CODE_MATERIAL, MICRO_DESC_MATERIAL, MICRO_TOTAL_D, MICRO_TOTAL_E, MICRO_TOTAL_F)
select ...
, case when #MICRO_CODE_MATERIAL != '---' then #MICRO_CODE_MATERIAL else null end
, case when #MICRO_DESC_MATERIAL != '---' then #MICRO_CODE_MATERIAL else null end
, try_convert(int, #MICRO_TOTAL_D)
, try_convert(int, #MICRO_TOTAL_E)
, try_convert(int, #MICRO_TOTAL_F)
However if you are passing this data from a client application then convert it client side.