I am trying to achieve a keyword search from my whole MySQL DB via JSP, I am confused if the method I chose is inefficient :(
I've read about the information_schema and found all column labels are there.
I've tried the SQL statement below to generate all the possible queries:
SELECT CONCAT('SELECT * FROM ',table_schema,'.',table_name,
' WHERE ',column_name,' LIKE ','searchString',';')
FROM information_schema.columns
WHERE table_schema NOT IN ('information_schema','mysql','performance_schema')
AND (column_type LIKE 'char(%'
OR column_type LIKE 'varchar(%'
OR column_type LIKE '%text')
and tried JSP code to get all the data match possible.
<%
String searchString = "malayalam";
searchString = "''%"+searchString+"%'' ";
ArrayList<String> queries = new ArrayList<String>();
String sql="SELECT CONCAT('SELECT * FROM ',table_schema,'.',table_name,"
+ "' WHERE ',column_name,' LIKE ','"+searchString+"',';')"
+ "FROM information_schema.columns "
+ "WHERE table_schema NOT IN ('information_schema','mysql','performance_schema')"
+ "AND (column_type LIKE 'char(%'"
+ "OR column_type LIKE 'varchar(%'"
+ "OR column_type LIKE '%text')";
try{
DBConInfoSchema db = new DBConInfoSchema();
ResultSet rs = db.getData(sql);
while(rs.next()){
queries.add(rs.getString(1));
}
for(int i=0;i<queries.size();i++){
DBConInfoSchema dCon = new DBConInfoSchema();
ResultSet rsDemo = dCon.getData(queries.get(i));
if(rsDemo.next()){
out.print("<br/>Data found n query-"+i+" -> "+queries.get(i));
}
dCon.DBClose();
}
}catch(Exception w){
out.print("excep<br/>"+w);
}
%>
Now I got huge list of Queries.
I am confused if its Good or Bad?!
Is this bad method when considering efficiency?
In the query building section
SELECT CONCAT('SELECT * FROM ',table_schema,'.',table_name,
' WHERE ',column_name,' LIKE ','searchString',';')
FROM information_schema.columns
WHERE table_schema NOT IN ('information_schema','mysql','performance_schema')
AND (column_type LIKE 'char(%'
OR column_type LIKE 'varchar(%'
OR column_type LIKE '%text')
I have updated line
WHERE table_schema NOT IN ('information_schema','mysql','performance_schema')
to
WHERE table_schema IN ('<my_table_name>')
to generate all the search results in my_table_name and saved to ArrayList and executed them
ArrayList<String> queries = new ArrayList<String>();
DBConInfoSchema db = new DBConInfoSchema();
ResultSet rs = db.getData(sql_statement);
while(rs.next()){
queries.add(rs.getString(1));
}
from there I sorted out the required data.
-Hope this may help some one.
NB: Even though it worked for me I still believe its Naive
Correct me If there's a better way yo achieve this
Related
I have connected Java to SSMS and can call data from the server no problems using something like this:
String cell = "SELECT [Close] FROM ExcelData WHERE id_num = 3";
Statement st4 = con.createStatement();
ResultSet rs4 = st4.executeQuery(cell);
while (rs4.next())
{
Float close = rs4.getFloat("close");
System.out.format("%s\n", close);
}
When I replace the "SELECT [Close] FROM ExcelData WHERE id_num = 3" to "SELECT #SMA" I get the much questioned "Must declare the scalar variable #SMA.
I do not know how to do that.
Answering my own question to help others who may need to know this...
It cannot be done. The work around is to create a table in SQL and insert the variable into the table.
DROP TABLE IF EXISTS SMA
CREATE TABLE SMA (
SMA_Price DECIMAL (6,5),
)
INSERT INTO SMA VALUES (#SMA);
SELECT * FROM SMA;
You can then call "SELECT * FROM SMA" from Java.
I am trying to read a temporary variable created from my MySql query as follows:
String name = "";
selectQuery = "select (select "
+ "CONCAT(s.firstname,\" \",s.surname) "
+ "AS name) "
+ "from student s, marks m where m.grade = 'fail'";
try{
pstmt = con.prepareStatement(selectQuery);
rs = pstmt.executeQuery(selectQuery);
int count = 0;
while(rs.next()){
name = rs.getString("name");
System.out.println(++count+". "+name);
}
rs.close();
pstmt.close();
}catch(Exception e){
e.printStackTrace();
}
I get SQLException as column 'name' not found. When I run the query in MySql server it runs fine.
In order for the alias to apply, it must be places outside the nested query's parenthesis, not inside it. However, you could just drop it altogether and just use the concat call directly in the select list.
Two more side notes:
Implicit joins (i.e., placing more than one table in the from list) have been deprecated for quite a while. It's considered a better practice to use explicit joins.
Regardless of the joining syntax you're using, you're missing the join condition.
Using concat_ws instead of concat may save you some hassle with handling the white space yourself.
To make a long story short:
select CONCAT_WS(' ', s.firstname, s.surname) AS name
FROM student s
JOIN marks m ON s.id = m.student_id
WHERE m.grade = 'fail'
I was wondering if using PreparedStatement.setString() was a good idea (possible, sensible?) to dynamically build a query.
For example :
sql code:
SELECT * FROM table1 WHERE table1.category = ? ?
java code:
ps.setString(1,"category1");
ps.setString(2,"AND table1.category = 'category2'");
Also, would it be possible to do something like:
ps.setString(1,"category1");
ps.setString(2," AND table1.category = ?");
ps.setString(3,"category2");
Best regards
Unfortunately, NO.
PreparedStatements are strictly for values only. Table Names and Column Names (as well as conditions in your example) are not allowed. So the best way to do is to concatenate it with the string.
String others = " AND table1.category = ?";
String query = "SELECT * FROM table1 WHERE table1.category = ? " + others;
java code:
ps.setString(1,"category1");
ps.setString(2,"category2");
Whatever you put inside setString will go within single quotes ' ' and will not be interpreted as a query.
I am trying to use a MapSqlParameterSource to create a query using a Like clause.
The code is something like this. The function containing it receives nameParam:
String namecount = "SELECT count(*) FROM People WHERE LOWER(NAME) LIKE :pname ";
String finalName= "'%" +nameParam.toLowerCase().trim() + "%'";
MapSqlParameterSource namedParams= new MapSqlParameterSource();
namedParams.addValue("pname", finalName);
int count= this.namedParamJdbcTemplate.queryForInt(namecount, namedParams);
This does not work correctly, giving me somewhere between 0-10 results when I should be receiving thousands. I essentially want the final query to look like:
SELECT count(*) FROM People WHERE LOWER(NAME) LIKE '%name%'
but this is evidently not happening. Any help would be appreciated.
Edit:
I have also tried putting the '%'s in the SQL, like
String finalName= nameParam.toLowerCase().trim();
String namecount = "SELECT count(*) FROM People WHERE LOWER(NAME) LIKE '%:pname%' "
;
but this does not work either.
You don't want the quotes around your finalName string. with the named parameters you don't need to specify them. This should work:
String namecount = "SELECT count(*) FROM People WHERE LOWER(NAME) LIKE :pname ";
String finalName= "%" + nameParam.toLowerCase().trim() + "%";
MapSqlParameterSource namedParams= new MapSqlParameterSource();
namedParams.addValue("pname", finalName);
int count= this.namedParamJdbcTemplate.queryForInt(namecount, namedParams);
This solution worked for me. I put the "%" on the Object[] parameters list:
String sqlCommand = "SELECT customer_id, customer_identifier_short, CONCAT(RTRIM(customer_identifier_a),' ', RTRIM(customer_identifier_b)) customerFullName "
+ " FROM Customer "
+ " WHERE customer_identifier_short LIKE ? OR customer_identifier_a LIKE ? "
+ " LIMIT 10";
List<Customer> customers = getJdbcTemplate().query(sqlCommand, new Object[] { query + "%", query + "%"}, new RowMapper<Customer>() {
public Customer mapRow(ResultSet rs, int i) throws SQLException {
Customer customer = new Customer();
customer.setCustomerFullName(rs.getString("customerFullName"));
customer.setCustomerIdentifier(rs.getString("customer_identifier_short"));
customer.setCustomerID(rs.getInt("customer_id"));
return customer;
}
});
return customers;
Have you tried placing the % wild cards in your sql string (not the bind variable value itself):
String finalName= nameParam.toLowerCase().trim();
String namecount = "SELECT count(*) FROM People WHERE LOWER(NAME) LIKE '%:finalName%'";
We can use simple JdbcTemplate instead of NamedParamJdbcTemplate
String namecount = "SELECT count(*) FROM People WHERE LOWER(NAME) LIKE ? ";
String finalName= "%" +nameParam.toLowerCase().trim() + "%"; //Notes: no quote
getJdbcTemplate().queryForInt(namecount, new Object[] {finalName});
Hope it helpful for someone using JdbcTemplate
Sometimes you have to write some of your queries in native SQL rather than hibernate HQL. Is there a nice way to avoid hardcoding table names and fields and get this data from existing mapping?
For example instead of:
String sql = "select user_name from tbl_user where user_id = :id";
something like:
String sql = "select " + Hibernate.getFieldName("user.name") + " from " + Hibernate.getTableName(User.class) + " where " + Hibernate.getFieldName("user.id") + " = :id";
It is possible to get this information as shown below, but I am not sure that I would do this in production code unless I really need the table names to be changeable after the code has been compiled. Otherwise, is it really worth the readability cost to your code to have this?
AbstractEntityPersister metadata =
(AbstractEntityPersister) sessionFactory.getClassMetadata(User.class);
String tableName = metadata.getTableName();
String[] columnNames = metadata.getKeyColumnNames();