Android Question How to convert SQL statements in B4A?

[bskotu555]

'cx' and 'zw' are text variables：
strSQL ="SELECT * FROM smt where cxnm='" & cx & "' and zwnm='" & zw & "'"
Cursor = Starter.Mysql_Jdbc.ExecQuery(strSQL)

 

[walt61]

Similar to https://www.b4x.com/android/forum/t...ified-conditions-a-and-b.163731/#post-1004256 :

strSQL ="SELECT * FROM smt where `cxnm`=? and `zwnm`=?"
Cursor = Starter.Mysql_Jdbc.ExecQuery2(strSQL, Array As String(cx, zw))

 

[bskotu555]

Similar to https://www.b4x.com/android/forum/t...ified-conditions-a-and-b.163731/#post-1004256 :

strSQL ="SELECT * FROM smt where `cxnm`=? and `zwnm`=?"
Cursor = Starter.Mysql_Jdbc.ExecQuery2(strSQL, Array As String(cx, zw))

The statement is incorrect here. The symbols' and ',' and 'should be placed next to each other

 

[walt61]

Did you use backticks or single quotes? They're not the same character!

 

[bskotu555]

Did you use backticks or single quotes? They're not the same character!

I put these two sentences into the program, but it just reported an error. What's the situation?

 

[aeric]

View attachment 158030
I put these two sentences into the program, but it just reported an error. What's the situation?

If your column names are English word without blank spaces, then you don't need to escape them with back ticks.
Just write like this will do:

Dim strSQL As String = "SELECT * FROM smt WHERE cxnm = ? AND zwnm = ?"

 

[walt61]

If your column names are English word without blank spaces, then you don't need to escape them with back ticks.

You are of course absolutely right. I make it a habit of using backticks for column and table names: then, I don't have to worry about them being reserved words or containing special characters.

 

[walt61]

View attachment 158030
I put these two sentences into the program, but it just reported an error. What's the situation?

You have a NullPointerException. Possibly, your Mysql_Jdbc has not been initialised.

 

[bskotu555]

I made a low-level mistake: the SMT database does not exist, I replaced it with a program, and after making the necessary changes, it will be fine.

You have a NullPointerException. Possibly, your Mysql_Jdbc has not been initialised.