ISNULL(expression, replacement)这里，expression是列名，而replacement是当列值为NULL时将替换该列的值。在下面的例子中，我们检索产品颜色、尺寸和类别的数据，并用预定义值Unknown替换 NULL ：SELECT Name,ISNULL(NULLIF(LTRIM(RTRIM(Color)), ''), 'Unknown') AS Color,ISNULL(NULLIF(LTRIM(RTRIM(Size)), '...
PERCENTILE_CONT :返回一个与输入的分布百分比值相对应的数据值 RATIO_TO_REPORT :该函数计算expression/(sum(expression))的值,它给出相对于总数的百分比 REGR_ (Linear Regression) Functions :这些线性回归函数适合最小二乘法回归线,有9个不同的回归函数可使用 代码语言:javascript 代码运行次数:0 运行 AI代码解...
NULLNULL is an untyped constant representing the unknown value. Allowed in CAST expressions or in INSERT VALUES lists and UPDATE SET clauses. Using it in a CAST expression gives it a specific data type. Dynamic parameterA dynamic parameter is a parameter to an SQL statement for which the valu...
Example 2-51 Simple CASE Expression with WHEN NULL 代码语言:javascript 代码运行次数:0 运行 AI代码解释 DECLAREgradeCHAR(1);--NULLbydefaultappraisalVARCHAR2(20);BEGINappraisal:=CASEgradeWHENNULLTHEN'No grade assigned'WHEN'A'THEN'Excellent'WHEN'B'THEN'Very Good'WHEN'C'THEN'Good'WHEN'D'THEN'Fair...
定义Node,包括Expression,Relation,Statement,SelectItem等,具体如下所示: SQL Parser SQL parser 将SQL语法转化为AST, 可以通过Antlr4 Visitor模式实现,核心Parse逻辑如下: public class SqlParser { public Statement createStatement(String sql) { return (Statement) invokeParser("statement", sql, SparrowSQLParser:...
Foreign Key (属性名) References 表名(属性名) [ON DELETE[CASCADE|SET NULL]] ON DELETE CASCADE 表示删除被参照关系的元组时,同时删除参照关系中的元组; ON DELETE SET NULL表示删除被参照关系的元组时,将参照关系的相应属性值置为空值。 属性值上的约束 ...
功能：测试NULL值：IFNULL函数的主要功能是检查其第一个参数是否为NULL。返回适当表达式：如果第一个参数为NULL，则返回第二个参数的值；否则，返回第一个参数的值。参数：SQL通用函数：允许三个参数。当expression1不为空时，如果指定了expression3且其长度、精度或比例与expression2不同，则可能返回...
The only exception to this rule is the LIKE predicate. When the right side of a LIKE predicate expression features a value with a trailing space, SQL Server does not pad the two values to the same length before the comparison occurs. Because the purpose of the LIKE predicate, by definition...
[Internet Tax Amount]) //Will true for any null or zero value //To be clear: the expression 0=null always returns true in MDX MEMBER MEASURES.IsZero AS [Measures].[Internet Tax Amount]=0 SELECT {[Measures].[Internet Tax Amount],MEASURES.ISEMPTYDemo,MEASURES.IsZero} ON COLUMNS, [...
function_call ( expression [ , ...n ] ) [ [ AS ] table_alias ] [ (column_alias [ , ...n ] ) ] } <tablesample_clause> ::= TABLESAMPLE [ SYSTEM ] ( sample_number [ PERCENT | ROWS ] ) [ REPEATABLE ( repeat_seed ) ] <joined_table> ::= { <join_type> ON <search_con...