Queries and Aggregations is basically formed by using Get, Find, Count methods, with conjunction of following chainable APIs to form conditions, grouping and ordering:
查询和统计主要使用Get, Find, Count三个方法。在进行查询时可以使用多个方法来形成查询条件，条件函数如下：
Id([]interface{}) Primary Key lookup
Where(string, …interface{}) As SQL conditional WHERE clause
And(string, …interface{}) Conditional AND
Or(string, …interface{}) Conditional OR
Sql(string, …interface{}) Custom SQL query
Asc(…string) Ascending ordering on 1 or more fields
Desc(…string) Descending ordering on 1 or more fields
OrderBy(string) As SQL ORDER BY
In(string, …interface{}) As SQL Conditional IN
Cols(…string) Explicity specify query or update columns. e.g.,:
engine.Cols("age", "name").Find(&users)
// SELECT age, name FROM user
engine.Cols("age", "name").Update(&user)
// UPDATE user SET age=? AND name=?
Omit(...string) Inverse function to Cols, to exclude specify query or update columns. Warning: Don't use with Cols()
engine.Omit("age").Update(&user)
// UPDATE user SET name = ? AND department = ?
Distinct(…string) As SQL DISTINCT
engine.Distinct("age", "department").Find(&users)
// SELECT DISTINCT age, department FROM user
Caution: this method will not lookup from caching store
Table(nameOrStructPtr interface{}) Specify table name, or if struct pointer is passed into the name is extract from struct type name by IMapper conversion policy
Limit(int, …int) As SQL LIMIT with optional second param for OFFSET
Top(int) As SQL LIMIT
Join(type, tableName, criteria string) As SQL JOIN, support type: either of these values [INNER, LEFT OUTER, CROSS] are supported now tableName: joining table name criteria: join criteria
GroupBy(string) As SQL GROUP BY
Having(string) As SQL HAVING