'Data type mismatch in criteria expression' with LabVIEW database query

Question

I have two tables:

table 1 : info1 -> where i have pid(primary key),name,address,sex etc.

table 2 : visit -> where i have the pid(foreign key), visit_date,next_visit,details

I used a query

SELECT info1.Patient_ID, visit.Visit_Date, visit.Next_Visit, 
visit.Visit_Details from info1, visit WHERE info1.Patient_ID ="%"

Is this query correct??

LabVIEW code:

Front panel:

Table 1 (info1):

Table 2 (visit):

Error:

Answer 1

Your query needs a JOIN:

SELECT info1.Patient_ID, visit.Visit_Date, visit.Next_Visit, visit.Visit_Details 
FROM info1 INNER JOIN visit ON info1.Patient_ID = visit.Patient_ID
WHERE info1.Patient_ID ="%"

If you use an INNER JOIN as shown above, then you'll only get a result for Patient_ID's that have an entry in both of the two tables. If you wanted to see all Patient_ID's whether or not they had a visit record, for example, you would use a LEFT OUTER JOIN.

Note: in the LabVIEW code you've shown, you are constructing the query by building a string from user-supplied data (the Patient ID front panel control). This is a really bad idea because it enables SQL injection attacks by malicious users. You should look up how to supply the value as a parameter to your LabVIEW database functions instead.