If you are building Dynamic SOQL Queries that can be using for Apex Classes and Batch Apex you can use the Database.query(”) function to build the query:

      private static final String soqlQuery = 'Select id, OwnerId from Account';
      public void updateAccountOwnerByOwnerName(String currentOwnerName, String newOwnerName)
      {
         Map<Account> updateAccountWithNewOwnerName = new Map();
         List<Account> accountsAssignedToCurrentOwner = Database.query(soqlQuery + ' where Owner.Name like \' currentOwnerName + \');
         User getNewOwnerId = new User(Name=newOwnerName);
         for (Account accountsToUpdateOwner : accountsAssignedToCurrentOwner)
         {
           accountsToUpdateOwner.OwnerId = getNewOwnerId.Id;
           updateAccountWithNewOwnerName.put(accountsToUpdateOwner.OwnerId, accountsToUpdateOwner);
         }
        update updateAccountWithNewOwnerName.values();
      }

Non-dynamic soql or static soql looks like:

List<Account> accounts = [select id from account limit 100];

Apex Batch returns Database.QueryLocator or a Iterable.

private String query = 'Select id from Account';
return Database.getQueryLocator(query);

Combining non-dynamic SOQL with dynamic SOQL by converting from [ ] to a String. Using Database.getQueryLocator this can be done:

Database.getQueryLocator([select id from account] + ' where Owner.Name =' + newOwnerName);