sql.append()方法是什么
时间: 2023-12-06 21:45:35 浏览: 180
在Python中,`sql.append()`是用于向列表(list)对象中添加新元素的方法。具体来说,它将传递给它的参数添加到列表的末尾。这个方法不会返回任何值,只是修改了原始列表对象。
例如,我们可以创建一个空列表,然后使用`append()`方法将一些元素添加到其中:
```
sql = []
sql.append("SELECT * FROM users;")
sql.append("INSERT INTO users (name, age) VALUES ('Alice', 25);")
```
在这个例子中,我们首先创建了一个空列表`sql`,然后使用`append()`方法向该列表中添加两个字符串,分别表示一个查询和一个插入操作。现在,`sql`列表包含两个元素,可以在后续的代码中使用它们来执行数据库操作。
相关问题
StringBuilder sql = new StringBuilder(" WHERE "); for (Map.Entry<String, String> entry : query.entrySet()) { if (entry.getKey().contains(FindConfig.MIN_)) { String min = humpToLine(entry.getKey()).replace("_min", ""); sql.append("`"+min+"`").append(" >= '").append(URLDecoder.decode(entry.getValue(), "UTF-8")).append("' and "); continue; } if (entry.getKey().contains(FindConfig.MAX_)) { String max = humpToLine(entry.getKey()).replace("_max", ""); sql.append("`"+max+"`").append(" <= '").append(URLDecoder.decode(entry.getValue(), "UTF-8")).append("' and "); continue; } if (like == true) { sql.append("`"+humpToLine(entry.getKey())+"`").append(" LIKE '%").append(URLDecoder.decode(entry.getValue(), "UTF-8")).append("%'").append(" and "); } else { sql.append("`"+humpToLine(entry.getKey())+"`").append(" = '").append(URLDecoder.decode(entry.getValue(), "UTF-8")).append("'").append(" and "); } } if (sqlwhere!=null && !sqlwhere.trim().equals("")) { sql.append(sqlwhere).append(" and "); } sql.delete(sql.length() - 4, sql.length()); sql.append(" "); return sql.toString(); 写一个相似的生成where后面条件查询的方法
可以参考以下代码:
```
public static String generateWhereClause(Map<String, String> query, boolean like, String sqlWhere) throws UnsupportedEncodingException {
StringBuilder sql = new StringBuilder(" WHERE ");
for (Map.Entry<String, String> entry : query.entrySet()) {
String key = entry.getKey();
String value = URLDecoder.decode(entry.getValue(), "UTF-8");
if (key.contains(FindConfig.MIN_)) {
String min = humpToLine(key).replace("_min", "");
sql.append("`").append(min).append("`").append(" >= '").append(value).append("' and ");
} else if (key.contains(FindConfig.MAX_)) {
String max = humpToLine(key).replace("_max", "");
sql.append("`").append(max).append("`").append(" <= '").append(value).append("' and ");
} else if (like) {
sql.append("`").append(humpToLine(key)).append("`").append(" LIKE '%").append(value).append("%'").append(" and ");
} else {
sql.append("`").append(humpToLine(key)).append("`").append(" = '").append(value).append("'").append(" and ");
}
}
if (sqlWhere != null && !sqlWhere.trim().equals("")) {
sql.append(sqlWhere).append(" and ");
}
sql.delete(sql.length() - 4, sql.length());
sql.append(" ");
return sql.toString();
}
private static String humpToLine(String str) {
Matcher matcher = Pattern.compile("[A-Z]").matcher(str);
StringBuilder builder = new StringBuilder(str);
int i = 0;
while (matcher.find()) {
builder.replace(matcher.start() + i, matcher.end() + i, "_" + matcher.group().toLowerCase());
i++;
}
if (builder.charAt(0) == '_') {
builder.deleteCharAt(0);
}
return builder.toString();
}
```
这段代码与之前的代码类似,但是有以下几个改进:
1. 将 `humpToLine` 方法提取出来,可以在其他方法中使用;
2. 将 `if-else if` 改为 `if-else`,可以让代码更加简洁;
3. 将解码逻辑提取出来,可以让代码更加清晰;
4. 代码中加入了一些空格,可以让生成的 SQL 更加美观。
Long id = billingWaterDTO.getBrokerEnterprise().getId(); StringBuilder sqlBuilder = new StringBuilder(); sqlBuilder.append("insert into billingwater (balance,billDate,feeType,iOFlag,iOmoney,remake,brokerEnterpriseFeeId) "); sqlBuilder.append("VALUES ("); sqlBuilder.append("(Select t.balance from "); sqlBuilder.append("(select balance"); sqlBuilder.append("-"); sqlBuilder.append(billingWaterDTO.getiOmoney()); sqlBuilder.append(" as balance from billingwater where brokerEnterpriseFeeId="); sqlBuilder.append(id); sqlBuilder.append(" ORDER BY id desc limit 0,1) t), "); if (billingWaterDTO.getBillDate() == null) { sqlBuilder.append("NOW(),'"); } else { sqlBuilder.append("'"); sqlBuilder.append(DateFormatUtils.format(billingWaterDTO.getBillDate(), DateUtil.DATE_TIME)); sqlBuilder.append("','"); } sqlBuilder.append(billingWaterDTO.getFeeType()); sqlBuilder.append("','"); sqlBuilder.append(billingWaterDTO.getiOFlag()); sqlBuilder.append("','"); sqlBuilder.append(billingWaterDTO.getiOmoney()); sqlBuilder.append("','"); sqlBuilder.append(billingWaterDTO.getRemake()); sqlBuilder.append("','"); sqlBuilder.append(id); sqlBuilder.append("')"); 改成jpa
可以使用JPA的EntityManager来进行插入操作,首先需要在实体类上添加@Entity注解,并且在实体类中添加对应的属性和getter/setter方法。例如,假设实体类为BillingWater:
```
@Entity
@Table(name = "billingwater")
public class BillingWater {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private BigDecimal balance;
@Column(name = "billDate")
private Date billDate;
@Column(name = "feeType")
private String feeType;
@Column(name = "iOFlag")
private String iOFlag;
@Column(name = "iOmoney")
private BigDecimal iOmoney;
private String remake;
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "brokerEnterpriseFeeId")
private BrokerEnterprise brokerEnterprise;
// 省略getter/setter方法
}
```
然后可以在对应的Repository中定义插入方法,例如:
```
public interface BillingWaterRepository extends JpaRepository<BillingWater, Long> {
@Modifying
@Query(value = "insert into billingwater (balance,billDate,feeType,iOFlag,iOmoney,remake,brokerEnterpriseFeeId) " +
"VALUES (:balance, :billDate, :feeType, :iOFlag, :iOmoney, :remake, :brokerEnterpriseFeeId)", nativeQuery = true)
void insertBillingWater(@Param("balance") BigDecimal balance,
@Param("billDate") Date billDate,
@Param("feeType") String feeType,
@Param("iOFlag") String iOFlag,
@Param("iOmoney") BigDecimal iOmoney,
@Param("remake") String remake,
@Param("brokerEnterpriseFeeId") Long brokerEnterpriseFeeId);
}
```
然后在插入之前可以判断字段是否为空,例如:
```
if(StringUtils.isNotBlank(billingWaterDTO.getBrokerEnterprise().getId().toString())
&& StringUtils.isNotBlank(billingWaterDTO.getFeeType())
&& StringUtils.isNotBlank(billingWaterDTO.getiOFlag())
&& billingWaterDTO.getiOmoney() != null) {
// 执行插入操作
BillingWater billingWater = new BillingWater();
BigDecimal balance = entityManager.createNativeQuery("select balance - :iOmoney as balance from billingwater where brokerEnterpriseFeeId = :id order by id desc limit 0,1")
.setParameter("iOmoney", billingWaterDTO.getiOmoney())
.setParameter("id", billingWaterDTO.getBrokerEnterprise().getId())
.getSingleResult();
billingWater.setBalance(balance);
billingWater.setFeeType(billingWaterDTO.getFeeType());
billingWater.setiOFlag(billingWaterDTO.getiOFlag());
billingWater.setiOmoney(billingWaterDTO.getiOmoney());
billingWater.setRemake(billingWaterDTO.getRemake());
billingWater.setBrokerEnterprise(brokerEnterpriseRepository.findById(billingWaterDTO.getBrokerEnterprise().getId()).orElse(null));
if (billingWaterDTO.getBillDate() == null) {
billingWater.setBillDate(new Date());
} else {
billingWater.setBillDate(billingWaterDTO.getBillDate());
}
billingWaterRepository.save(billingWater);
}
```
其中,使用EntityManager的createNativeQuery()方法执行原生SQL查询,然后获取查询结果并设置到实体类中,最后使用JpaRepository的save()方法进行保存操作。
需要注意的是,在使用JpaRepository进行插入操作时,需要在对应的方法上添加@Modifying注解和@Query注解,并且将nativeQuery属性设置为true,表示使用原生SQL语句进行操作。同时,在设置参数时需要使用@Param注解来指定参数的名称。