PL/pgSQL is a procedural language similar to Oracle's PL/SQL. It's much more powerful than pure SQL in that it supports variables, conditional expressions, looping constructs, exceptions, and the like. Because it natively supports all of PostgreSQL's SQL syntax, you can consider it a supers...
包括join */Node *whereClause;/* where子句 */List *groupClause;/* GROUP BY clauses */Node *havingClause;/* HAVING conditional-expression */List *windowClause;/* WINDOW window_name AS (...), ... */List *sortClause
The CASE WHEN expression is used to implement conditional logic in SQL queries. It evaluates conditions and returns specific results based on whether the condition is true or false. It's commonly used in SELECT statements, but can also be used in WHERE, ORDER BY, and other SQL clauses. Syn...
the IF-THEN conditional ends with a final END statement. Conditional expressions in PL/pgSQL can be any SQL expression that you might use in the WHERE clause of a typical SELECT statement. The nice thing here, however, is that you...
What is CASE Statement and How to Write it in Postgres? As stated earlier, the CASE statement is a conditional expression, so it can be used with any statement or clause where an expression can be used, such as a WHERE clause, SELECT statement, etc. Postgres supports two forms of the ...
[where condition]; 多表插入语句(Multitable Insert Statements) insert [all] [conditional_insert_clause] [insert_into_cause values_clause](subquery) conditional_insert_clause [all][first] [when condition then][insert_into_clause values_clause] [else][insert_into+clause values_clause] 列: intsert...
HAVING Clause The HAVING clause is used to specify which individual group(s) are to be displayed, that is , the desire groups that you return on the basis of aggregate functions. The where clause cannot be used to get return the desire groups. The WHERE clause can only use to restrict ...
PostgreSQLINSERT FROM SELECTsyntax is mostly compatible with the Oracle syntax, except for a few Oracle-only features such as the conditional_insert_clause (ALL|FIRST|ELSE). Also, PostgreSQL doesn’t support the Oracle error_logging_clause. As an alternative, PostgreSQL provides th...
*/char*filename;/* filename, or NULL for STDIN/STDOUT */List*options;/* List of DefElem nodes */Node*whereClause;/* WHERE condition (or NULL) */}CopyStmt; 权限检查 进入到DoCopy函数后,需要进行初步的权限检查。首先需要做判断的是从文件/进程导入的场景:如果是从文件导入,那么当前用户需要有读...
select_no_parens: simple_select { $$ = $1; } // 简单查询语句 | select_clause sort_clause {...} // 排序从句 |... ; simple_select: SELECT opt_all_clause opt_target_list into_clause from_clause where_clause group_clause having_clause window_clause {...} | SELECT distinct_clause ta...