2020-11-27 How to Select All Fi

根据项目需求，我们需要动态配置数据，所以在SOQL语句中，我们要获得所有的字段，然后找到了下面的解决方案，具体参考下面的代码：

 public String getFieldsSOQL(String objectName){
        String selects = '';
        // Get a map of field name and field token
         Map<String, Schema.SObjectField> fMap = Schema.getGlobalDescribe().get(objectName.toLowerCase()).getDescribe().Fields.getMap();      
         list<string> selectFields = new list<string>();
         if (fMap != null) {
             for (Schema.SObjectField ft : fMap.values()) { // loop through all field tokens (ft)
                 Schema.DescribeFieldResult fd = ft.getDescribe(); // describe each field (fd)
                     selectFields.add(fd.getName());   
             }
         }
         if (!selectFields.isEmpty()) {
             for (string s:selectFields) {
                 selects += s + ',';
             }
             if (selects.endsWith(',')) {
                 selects = selects.substring(0,selects.lastIndexOf(','));
             }            
         }
        if (selects == null || selects == '') {
         selects = 'id';
         }
         return selects;  
    } 

通过下面的代码可以得到字段拼接的字符串，在Apex中使用的时候需要拼接SOQL语句，参考如下的用法：

        String selects = getFieldsSOQL();
        String query = 'SELECT '+selects +' FROM Lead';
        List<Lead> leadList = Database.getQueryLocator(query);