那么实际上,在这里,USE_CONCAT和NO_EXPAND成了互为"反函数"。在使用了NO_EXPAND提示后,从Oracle8之后,Oracle会使用"inlist iterator" 方式来执行SQL,这样可以用到index。 http://www.eygle.com/sql/How.to.Use.USE_CONCAT.hints.in.Oracle.htm
CONCAT and CONCAT_WS function in SQL Server Concatenate SQL Server Columns into a String with CONCAT() SQL CONCAT
sqlcmd is a command-line utility for ad hoc, interactive execution of Transact-SQL (T-SQL) statements and scripts and for automating T-SQL scripting tasks. To use sqlcmd interactively, or to build script files for sqlcmd, you should understand T-SQL. You can use sqlcmd in various ways....
3 2 INDEX (UNIQUE SCAN) OF 'PK_EMP' (UNIQUE) (Cost=1 Card=14) 4 1 TABLE ACCESS (BY INDEX ROWID) OF 'EMP' (Cost=2 Card=1 Bytes=37) 5 4 INDEX (UNIQUE SCAN) OF 'PK_EMP' (UNIQUE) (Cost=1 Card=14) --使用use_concat提示以后,Oracle将in-lists条件展开为两个查询块,分别使用索引...
String sqlUpdate = "update student set name = concat(name , 'copy')"; //3.ResultSet类,用来存放获取的结果集!! statement.executeUpdate(sqlUpdate); sql = "select * from student"; //3.ResultSet类,用来存放获取的结果集!! rs = statement.executeQuery(sql); ...
The aggregate dimension of the data row whose GROUPING__ID is 3 is province. SQL Implementation -- SQL - 6 with group_dimension as ( select -- Dimension fields corresponding to each group gb.group_id, concat_ws(",", collect_list(case when gb.placeholder_bit = 0 then dim_col.val else...
-- Declare variables to hold the dynamic columns (cols) and the final SQL query DELIMITER $ CREATE PROCEDURE dynamic_pivot() BEGIN DECLARE cols VARCHAR(1000); DECLARE sql_query VARCHAR(2000); -- Get the list of distinct years SELECT GROUP_CONCAT(DISTINCT CONCAT('SUM(CASE WHEN year = ', ...
SQL Server SUBSTRING Syntax SUBSTRING (expression, startPosition, length) Parameters expression– Input string used to get a portion of the string startPosition– Position number used to start getting the substring length –Number of characters for the length of the substring ...
We can use SQL SELECT Distinct to find unique references of data. For example, we have a result set that shows different rows of a table and each row consists of columns. Now sometimes we are more interested in unique patterns of the data rather than the data itself which is one of the...
3 rows in set (0.00 sec) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 注意:这里用到CONCAT()函数,用来把字符串串接起来。另外,我们还用到以前学到的AS给结果列'CONCAT(f_name, " ", l_name)'起了个假名。 5.1创建数据表 命令:create ...