Trying to make Java method to get the length of a column

[Joel Christophel]

Here's what I've tried. The 'rs' variable references a ResultSet object, and the 'meta' variable references a DatabaseMetaData object.

public static int getColumnLength(String tableName, String columnName){
	int columnLength = 0;
	
	try {
	    rs = meta.getColumns(null, null, tableName, columnName);
	    while (rs.next()) {
		columnLength = rs.getInt("COLUMN_SIZE");
	    }
	} catch (SQLException e) {
	    e.printStackTrace();
	}
	
	return columnLength;
    }

The column I'm trying to access contains 3 rows with the values being "Joel", "Hannah", and "Kevin. Since I'm trying to get the size of the column, my desired return value would be 3, but it's returning 25.

[Bear Bibeault]

That's because the size of a column is its length. It has nothing whatsoever to do with the number of rows.

In fact, the number of rows has nothing at all to do with a specific column but the table as a whole.

If you want to get the number of rows, you'd do that with a SELECT COUNT(*) statement.

[Rob Spoor]

If you want to exclude records with NULL values you should replace that COUNT(*) with COUNT(name_of_column).

[Joel Christophel]

Thanks for the help; it now returns 3. My new method:

    public static int getColumnLength(String tableName, String columnName){
	int columnLength = 0;
	String sql = "SELECT COUNT(" + columnName + ") FROM " + tableName;
	
	try {
	    rs = statement.executeQuery(sql);
	    while (rs.next()) {
		columnLength = rs.getInt(1);
	    }
	} catch (SQLException e) {
	    e.printStackTrace();
	}
	
	return columnLength;
    }