Hi,
I'm using node-tds in order to connect to Microsoft SQL database.
I have table A and B and a n to n relationship called C.
In order to insert something in table C I must check if the primary key of
A and B exist in their respective tables before with a SELECT statement.
Is there any sample code that does that?
I'm thinking something like this:
Select from table A
Check if values where returned.
If so, select from table B
Otherwise, insert into A
If B returned something, insert into C
Otherwise, insert into B
But if I get this last line I'll not insert into C. How to code
asynchronously? Any example on the website?
I wrote this code below, but it seems it's not working properly. It calls
only addA() and gives me error in tds.js (140) - if
(this._currentStatement) throw new Error('Statement currently running'):
function addA (a)
{
var stmtA = conn.createStatement('INSERT INTO A (id) VALUES (' + a +
')');
stmtA.execute();
}
function addB (space)
{
var stmtB = conn.createStatement('INSERT INTO B (id) VALUES (' + b +
')');
stmtB.execute();
}
function addC (a, b)
{
var stmtC = conn.createStatement('INSERT INTO C (a, b, date) VALUES ('
+ a + ', ' + b + ', GETDATE())');
stmtC.execute();
}
exports.linkAandB = function(a, b) {
var stmtA = conn.createStatement('SELECT * FROM A WHERE id = ' + a);
stmtRadio.on('done', function(done) {
if (!done.hasRowCount || done.rowCount <= 0) {
addA(a);
}
var stmtB = conn.createStatement('SELECT * FROM B WHERE id = ' + b);
stmtB.on('done', function(done) {
if (!done.hasRowCount || done.rowCount <= 0) {
addB(b);
}
addC(a, b);
});
stmtB.execute();
});
stmtA.execute();
}
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