SQL中的 CASE 类似编程语言里的 if-then-else 语句,用做逻辑判断。可以用于SELECT语句中,也可以用在WHERE,GROUP BY 和 ORDER BY 子句;可以单独使用,也可以和聚合函数结合使用。 语法如下: CASE WHEN condition1 THEN result1 [WHEN condition2 THEN result2] [...] [ELS
GROUP BY 语句用于结合聚合函数,根据一个或多个列对结果集进行分组 SELECTcolumn_name,aggregate_function(column_name)FROMtable_nameWHEREcolumn_nameoperatorvalueGROUPBYcolumn_name; SELECT site_id, SUM(access_log.count) AS nums FROM access_log GROUP BY site_id; GROUP BY 多表连接 SELECT Websites.name,...
<GROUP BY 列名> 对查询结果分组 [HAVING <条件表达式>] 分组筛选条件 [ORDER BY 列名 [ASC | DESC> 对查询结果排序;ASC:升序 DESC:降序 例1: select student.sno as 学号, student.name as 姓名, course as 课程名, score as 成绩 from score,student where student.sid=score.sid and score.sid=:sid...
Here, our aggregate function is COUNT( ) and we are passing price as an argument(参数) to GROUP BY. SQL willcount the total number of apps foreach pricein the table. It is usually helpful to SELECT the column you pass as an argument to GROUP BY. Here we SELECT price and COUNT(*)....
table_alias] |OPENXML<openxml_clause>|derived_table[ [AS]table_alias] [ (column_alias[ , ...n ] ) ] |<joined_table>|<pivoted_table>|<unpivoted_table>| @variable [ [AS]table_alias] | @variable.function_call( expression [ , ...n ] ) [ [AS]table_alias] [ (column_alias[ ,...
SQL_GROUP_BY SQL_IDENTIFIER_CASE SQL_IDENTIFIER_QUOTE_CHAR SQL_INDEX_KEYWORDS SQL_INSERT_STATEMENT SQL_INTEGRITY SQL_KEYWORDS SQL_LIKE_ESCAPE_CLAUSE SQL_NON_NULLABLE_COLUMNS SQL_OJ_CAPABILITIES SQL_ORDER_BY_COLUMNS_IN_SELECT SQL_OUTER_JOINS SQL_PROCEDURES SQL_QUOTED_IDENTIFIER_CASE SQL_SCHEMA_USAGE...
为了一个查询还要创建两个函数,太复杂了吧. 不用函数, 先只对EMP_HISTORY做group by,再与其他两个小表做关联,与使用函数的原理是一样的, 效率比使用函数的写法还要高. 17. 使用表的别名(Alias) 当在SQL语句中连接多个表时,请使用表的别名并把别名前缀于每个Column上.这样一来,就可以减少解析的时间并减少那...
GetOwnerAliasIdFromSid CMEDCatalogOwner::LookupPrimaryIdInCatalog CMEDCacheEntryFactory::GetProxiedCacheEntryByAltKey CMEDCatalogOwner::GetProxyOwnerBySID CMEDProxyDatabase::GetOwnerBySID ISECTmpEntryStore::Get ISECTmpEntryStore::Get NTGroupInfo::`vector deleting destructor' </value> </Slot> <Slot ...
根据X/Open和SQL Access Group SQL CAE规范(1992)所进行的定义,SQLERROR返回SQLSTATE值。SQLSTATE值是包含五个字符的字符串,由2个字符的SQL错误类和3个字符的子类构成。五个字符包含数值或者大写字母, 代表各种错误或者警告条件的代码。成功的状态是由00000标识的。SQL
INVALID_SHARED_ALIAS_NAME、INVALID_STATEMENT_OR_CLAUSE、INVALID_WINDOW_SPEC_FOR_AGGREGATION_FUNC、LOCAL_MUST_WITH_SCHEMA_FILE、MERGE_WITHOUT_WHEN、MIGRATION_NOT_SUPPORTED、MISSING_CLAUSES_FOR_OPERATION、MV_ST_ALTER_QUERY_INCORRECT_BACKING_TYPE、NOT_ALLOWED_IN_FROM、NOT_ALLOWED_IN_PIPE_OPERATOR_WHERE、...