Writing dynamic soql

Dynamic SOQL refers to the creation of a SOQL string at run time with Apex code. Dynamic SOQL enables you to create more flexible applications. For example, you can create a search based on input from an end user or update records with varying field names.

Examples:

Using dynamic select fields:

List<String> fields = new List<String>{'name'};

String soql = 'select Id, ' + String.join(fields, ', ') + ' from Account';

List<Account> objLst = Database.query(soql);

for(Account a : objLst){

System.debug(a.name);

}

Using dynamic where value:

String myTestString = 'Prospect';

List<Account> sobjList = Database.query('SELECT Id, name FROM Account WHERE Type = :myTestString');

for(Account a : sobjList){

System.debug(a.name);

}

Account myVariable = new Account(Type='Prospect');

String resolvedField1 = myVariable.Type;

List<Account> sobjList = Database.query('SELECT Id, name FROM Account WHERE Type = :resolvedField1' );

for(Account a : sobjList){

System.debug(a.name);

}