What is the efficient way to retrieve(select) data from database? - mysql

Question

In my database contain about 2 millions rows. That contains collection of sentences in each rows(Not English language).
![Image of database][1]
As a example if user give 'abcd' ,that matched with both row 1,3. Therefor both should select.
Because of that huge time taken to data retrieve. I'm using following code to retrieve data. If any given word match with the database those rows should be select.
sb.append("SELECT Sentence FROM corpus Where ");
for(int k=0;k<wordList.size();k++){
sb.append( " Sentence like '%" + wordList.get(k) + "%' OR ");
}
sb.append(" 1=0");
rs2 = dbc.sqlExecute(sb.toString());
That selection word may be anywhere in the row. That may be front or middle or end. My problem is when user give some word phrase, huge time taken to select matched rows. Is there any proper way to speed my database retrieves? I think indexing may not work because of I'm not searching only the starting point of the rows. That matched words may contain anywhere in the rows. What is the efficient way to do this? Huge time taken to retrieve. Huge problem to me.Can anyone know proper way to do this?

Answer 1

You don't need for loop, just do like this:
sb.append("SELECT Sentence FROM corpus Where Sentence like '%");
sb.append(wordList);
sb.append("%'");

Answer 2

I believe the efficient solution is to use a PreparedStatement with a bind parameter and execute it in a loop. You could use a For-Each Loop, and for each word in wordList bind the parameter and then get a ResultSet (using a try-with-resources) and add the returned sentences to your List with something like
List<String> sentences = new ArrayList<>();
String sql = "SELECT Sentence FROM corpus WHERE Sentence LIKE ?";
PreparedStatement ps = null;
try {
ps = conn.prepareStatement(sql);
for (String word : wordList) {
ps.setString(1, String.format("%%%s%%", word));
try (ResultSet rs = ps.executeQuery()) {
sentences.add(rs.getString(1));
} catch (Exception e) {
e.printStackTrace();
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (ps != null) {
try {
ps.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
While a FULLTEXT index on the Sentence column is probably advisable, this method has the benefit using the query cache and reducing the size of your query. The OR clauses just muddy the situation, since you want the matching rows of any of them. You might also consider a Set<String> sentences.