Java SQL列插入

Question

I created a table with column actual & Predicted

I inserted a Array of size 220 into column in table using SQL & JAVA

st.execute("insert into host_1 (actual) values ('"+ac[j]+"')");

Now i try to insert predicted value

st.executeUpdate("insert into host_1 (exp_predict) values ('"+pre[i]+"')");

It get inserted from 221th row. I want it to be inserted from row0

Plz anyone help

Answer 1

An insert statement always creates a new row. If you want to set values to existing rows, you should use an update statement. Or, better yet still, insert both values at the same time:

// Assume, or check, that ac and pre are the same size:
int size = ac.length;

PreparedStatement ps = 
    myConnection.prepareStatement
    ("INSERT INTO host_1 (actual, exp_predict) VALUES (?, ?)");
for (int i = 0; i < size; ++i) {
    ps.setString(1, ac[i]);
    ps.setString(2, pre[i]);
    ps.addBatch();
}
ps.executeBatch();

Answer 2

"insert into host_1 (actual) values ('"+ac[j]+"')" 

Above inserts a entire row. Not just column.

Answer 3

What you should do is first insert the column actual, later update the rows inserted. Your first SQL is fine, you only need to modify the second.

st.executeUpdate("update host_1 set exp_predict = pre[i] where actual = ac[j]");

Answer 4

You should update host_1 with exp_predict in the same loop with the condition as like

for(int i = 0; i<221; i++){
 st.execute("insert into host_1 (actual) values ('"+ac[j]+"')");

 st.executeUpdate("update host_1 set exp_predict = '"+pre[i]+"' where 
 actual = '"+ac[j]+"'
}