Query and sqlitequery operations in sqlite

Query and sqlitequery operations in sqlite
The query () method splits the select statement into several components and serves as the input parameter of the method:
SQLiteDatabase db = databaseHelper. getWritableDatabase ();
Cursor cursor = db. query ("person", new String [] {"personid, name, age"}, "name like? ", New String [] {" % Chuanzhi % "}, null, null," personid desc "," 1, 2 ");

While (cursor. moveToNext ()){
Int personid = cursor. getInt (0); // obtain the value of the first column. The index of the first column starts from 0.
String name = cursor. getString (1); // obtain the value of the second column
Int age = cursor. getInt (2); // get the value of the third column
}
Cursor. close ();
Db. close ();
The above code is used to find records whose name field contains "intelligence" from the person table. matched records are sorted in descending order by personid. The first record is skipped for the sorted results and only two records are obtained.
Meanings of parameters in the query (table, columns, selection, selectionArgs, groupBy, having, orderBy, limit) method:
Table: table name. It is equivalent to the part after the select statement from keyword. For multi-table join queries, you can use commas to separate the two table names.
Columns: name of the column to be queried. It is equivalent to the part after the select keyword of the select statement.
Selection: the query Condition Clause, which is equivalent to the part after the where keyword of the select statement. The placeholder "?" can be used in the Condition Clause.
SelectionArgs: it corresponds to the placeholder value in the selection statement. The position of the value in the array must be the same as that of the placeholder in the statement. Otherwise, an exception occurs.
GroupBy: equivalent to the part after the select statement group by keyword
Having: equivalent to the part after the having keyword of the select statement
OrderBy: equivalent to the part after the select statement order by keyword, such as: personid desc, age asc;
Limit: Specifies the offset and the number of retrieved records, which is equivalent to the part following the limit keyword of the select statement.