Apex SOQL 查询中的潜在异常情况

分配给单个对象时，返回除单行之外的任何内容的查询将抛出 QueryException。

try {
    Account a = [SELECT Id FROM Account WHERE Name = 'Non-existent Account'];  
} catch (QueryException e) {
    // List has no rows for assignment to SObject
}

try {
    Account a = [SELECT Id FROM Account];  
} catch (QueryException e) {
    // List has more than 1 row for assignment to SObject
}

尝试使用你未在查询中包含的字段将抛出 SObjectException

Account a = [SELECT Id FROM Account LIMIT 1];
try {
    System.debug( a.Name );
} catch (SObjectException e) {
    // SObject row was retrieved via SOQL without querying the requested field: Name
}