如何在SQL字符串中插入多个where子句
如何在SQL字符串中插入多个where子句
提问于 2019-06-11 23:10:25
我正在使用一个带有SQL语法的Azure Cosmos NoSQL数据库。如何创建可以动态添加更多WHERE语句的SQL字符串？例如，如果我有两个where语句，我希望能够不必在"WHERE f.%s=@val“中为一个函数编写代码，然后使用"WHERE f.%s=@val1和f.%s=@val2”硬编码另一个函数。我希望最多有7条WHERE语句。
下面的代码查询一个属性(一个WHERE语句)和另一个查询两个属性(两个WHERE语句)。这涉及到大量的硬编码。与queryString的线路是我遇到麻烦的地方。
public Iterable<Document> queryForOneProperty(String databaseName, String
collectionName, String key, String val) {
FeedOptions queryOptions = getDefaultFeedOptions();
String collectionLink = String.format("/dbs/%s/colls/%s", databaseName, collectionName);
SqlParameterCollection paramCollection = new SqlParameterCollection();
paramCollection.add(new SqlParameter("@val", val));
SqlQuerySpec query = new SqlQuerySpec(String.format("SELECT * FROM %s f WHERE f.%s = @val", collectionName, key), paramCollection);
return query;
}
public Iterable<Document> queryForTwoProperties(String databaseName, String
collectionName, String[] keys, String[] vals) {
FeedOptions queryOptions = getDefaultFeedOptions();
String collectionLink = String.format("/dbs/%s/colls/%s", databaseName, collectionName);
SqlParameterCollection paramCollection = new SqlParameterCollection();
paramCollection.add(new SqlParameter("@val1", vals[0]));
paramCollection.add(new SqlParameter("@val2", vals[1]));
String queryString = String.format("SELECT * FROM %s f WHERE f.%s = @val1 AND f.%s = @val2", collectionName, keys[0], keys[1]);
SqlQuerySpec query = new SqlQuerySpec(queryString, paramCollection);
return query;
}“”“
回答 2
Stack Overflow用户
发布于 2019-06-11 23:37:33
您可以创建一个伪造的第一个条件，然后只添加和...
String condition = "WHERE 1 = 1";
if (some logic) {
condition += " AND x = 42";
}下面是一个查询工厂方法的简单示例
private final static String BASE_QUERY = "SELECT * FROM %s f WHERE 1 = 1";
public static String queryBuilder(String ... conditions) {
StringBuilder builder = new StringBuilder(BASE_QUERY);
for (String condition : conditions) {
builder.append(" ");
builder.append(condition);
}
return builder.toString();
}示例
System.out.println(queryBuilder("AND f.%s = @val1", "AND f.%s = @val2"));
System.out.println(queryBuilder("AND f.%s = @val1"));
System.out.println(queryBuilder());给出
SELECT * FROM %s f WHERE 1=1和f。%s= @val1和f。%s= @val2
SELECT * FROM %s f WHERE 1=1 AND f.%s = @val1
SELECT * FROM %s f WHERE 1= 1
Stack Overflow用户
发布于 2019-06-11 23:38:20
尝试此用法为空
SELECT * FROM %s f WHERE (@val1 is null or f.%s = @val1) AND (@val2 is null or f.%s = @val2) 页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/56546756
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