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语法定义

安全云脑 SECMASTER-DQL语法定义:DQL语句

DQL语句语法定义 query: values | { select | selectWithoutFrom | query UNION [ ALL ] query | query EXCEPT query | query INTERSECT query } [ ORDER BY orderItem [, orderItem ]* ] [ LIMIT { count | ALL } ] [ OFFSET start { ROW | ROWS } ] [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY] orderItem: expression [ ASC | DESC ] select: SELECT [ ALL | DISTINCT ] { * | projectItem [, projectItem ]* } FROM tableExpression [ WHERE booleanExpression ] [ GROUP BY { groupItem [, groupItem ]* } ] [ HAVING booleanExpression ] [ WINDOW windowName AS windowSpec [, windowName AS windowSpec ]* ] selectWithoutFrom: SELECT [ ALL | DISTINCT ] { * | projectItem [, projectItem ]* } projectItem: expression [ [ AS ] columnAlias ] | tableAlias . * tableExpression: tableReference [, tableReference ]* | tableExpression [ NATURAL ] [ LEFT | RIGHT | FULL ] JOIN tableExpression [ joinCondition ] joinCondition: ON booleanExpression | USING '(' column [, column ]* ')' tableReference: tablePrimary [ matchRecognize ] [ [ AS ] alias [ '(' columnAlias [, columnAlias ]* ')' ] ] tablePrimary: [ TABLE ] [ [ catalogName . ] schemaName . ] tableName | LATERAL TABLE '(' functionName '(' expression [, expression ]* ')' ')' | UNNEST '(' expression ')' values: VALUES expression [, expression ]* groupItem: expression | '(' ')' | '(' expression [, expression ]* ')' | CUBE '(' expression [, expression ]* ')' | ROLLUP '(' expression [, expression ]* ')' | GROUPING SETS '(' groupItem [, groupItem ]* ')' windowRef: windowName | windowSpec windowSpec: [ windowName ] '(' [ ORDER BY orderItem [, orderItem ]* ] [ PARTITION BY expression [, expression ]* ] [ RANGE numericOrIntervalExpression {PRECEDING} | ROWS numericExpression {PRECEDING} ] ')' matchRecognize: MATCH_RECOGNIZE '(' [ PARTITION BY expression [, expression ]* ] [ ORDER BY orderItem [, orderItem ]* ] [ MEASURES measureColumn [, measureColumn ]* ] [ ONE ROW PER MATCH ] [ AFTER MATCH ( SKIP TO NEXT ROW | SKIP PAST LAST ROW | SKIP TO FIRST variable | SKIP TO LAST variable | SKIP TO variable ) ] PATTERN '(' pattern ')' [ WITHIN intervalLiteral ] DEFINE variable AS condition [, variable AS condition ]* ')' measureColumn: expression AS alias pattern: patternTerm [ '|' patternTerm ]* patternTerm: patternFactor [ patternFactor ]* patternFactor: variable [ patternQuantifier ] patternQuantifier: '*' | '*?' | '+' | '+?' | '?' | '??' | '{' { [ minRepeat ], [ maxRepeat ] } '}' ['?'] | '{' repeat '}'

安全云脑 SECMASTER 语法定义
数据湖探索 DLI-CREATE TABLE语句:语法说明

语法说明 COMPUTED COLUMN 计算列是一个使用 “column_name AS computed_column_expression” 语法生成的虚拟列。它由使用同一表中其他列的非查询表达式生成，并且不会在表中进行物理存储。例如，一个计算列可以使用 cost AS price * quantity 进行定义，这个表达式可以包含物理列、常量、函数或变量的任意组合，但这个表达式不能存在任何子查询。在 Flink 中计算列一般用于为 CREATE TABLE 语句定义时间属性。处理时间属性可以简单地通过使用了系统函数 PROCTIME() 的 proc AS PROCTIME() 语句进行定义。另一方面，由于事件时间列可能需要从现有的字段中获得，因此计算列可用于获得事件时间列。例如，原始字段的类型不是 TIMESTAMP(3) 或嵌套在 JSON 字符串中。注意：定义在一个数据源表（ source table ）上的计算列会在从数据源读取数据后被计算，它们可以在 SELECT 查询语句中使用。计算列不可以作为 INSERT 语句的目标，在 INSERT 语句中，SELECT 语句的 schema 需要与目标表不带有计算列的 schema 一致。

数据湖探索 DLI DDL语法定义