查询构建器
原文：https://beego.wiki/docs/mvc/model/querybuilder/
Query Builder 查询构建器
Query Builder 查询生成器
QueryBuilder provides an API for convenient and fluent construction of SQL queries. It consists of a set of methods enabling developers to easily construct SQL queries without compromising readability.
QueryBuilder 提供了一个 API，用于方便且流畅地构建 SQL 查询。它由一组方法组成，使开发人员能够轻松构建 SQL 查询，而不会影响可读性。
It serves as an alternative to ORM. ORM is more for simple CRUD operations, whereas QueryBuilder is for complex queries with subqueries and multi-joins.
它作为 ORM 的替代品。ORM 更适用于简单的 CRUD 操作，而 QueryBuilder 适用于具有子查询和多重联接的复杂查询。
Usage example:
用法示例：
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| // User is a wrapper for result row in this example
type User struct {
Name string
Age int
}
var users []User
// Get a QueryBuilder object. Takes DB driver name as parameter
// Second return value is error, ignored here
qb, _ := orm.NewQueryBuilder("mysql")
// Construct query object
qb.Select("user.name",
"profile.age").
From("user").
InnerJoin("profile").On("user.id_user = profile.fk_user").
Where("age > ?").
OrderBy("name").Desc().
Limit(10).Offset(0)
// export raw query string from QueryBuilder object
sql := qb.String()
// execute the raw query string
o := orm.NewOrm()
o.Raw(sql, 20).QueryRows(&users)
|
Full API interface:
完整的 API 接口：
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| type QueryBuilder interface {
Select(fields ...string) QueryBuilder
ForUpdate() QueryBuilder
From(tables ...string) QueryBuilder
InnerJoin(table string) QueryBuilder
LeftJoin(table string) QueryBuilder
RightJoin(table string) QueryBuilder
On(cond string) QueryBuilder
Where(cond string) QueryBuilder
And(cond string) QueryBuilder
Or(cond string) QueryBuilder
In(vals ...string) QueryBuilder
OrderBy(fields ...string) QueryBuilder
Asc() QueryBuilder
Desc() QueryBuilder
Limit(limit int) QueryBuilder
Offset(offset int) QueryBuilder
GroupBy(fields ...string) QueryBuilder
Having(cond string) QueryBuilder
Update(tables ...string) QueryBuilder
Set(kv ...string) QueryBuilder
Delete(tables ...string) QueryBuilder
InsertInto(table string, fields ...string) QueryBuilder
Values(vals ...string) QueryBuilder
Subquery(sub string, alias string) string
String() string
}
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Now we support Postgress, MySQL and TiDB。
现在我们支持 Postgress 、 MySQL 和 TiDB 。