源代码：大批量SQL代码语法转换简单实例：ORACLE START WITH CONNECT 语法改写

### 背景：在不同数据库迁移的项目中，往往会遇到SQL语法不兼容的情况。

### 问题：如果存在大量代码需要改写的情况，靠人工处理会很耗时，且容易出错。能不能通过工具实现代码语法的大批量自动转换？

### 方案：可以使用开源代码解析器 ZGLanguage 对SQL代码进行大批量自动转换

### 案例演示：

# 假设 ORACLE START WITH CONNECT 语法代码（ start_with_connect.sql ）：

SELECT *
FROM tree 
START WITH id = 1
CONNECT BY NOCYCLE PRIOR id = parentid
;

# 配置转换规则可以将以上代码直接转换成如下代码（改写成with recursive语法）：

with recursive wr_tree as 
( 
SELECT id, parentid, 1 as level from tree where id = 1 
union 
SELECT tree.id, tree.parentid, level + 1 from tree, wr_tree where tree.parentid = wr_tree.id 
) 
SELECT * from wr_tree order by id
;

# 转换规则（ STATR_WITH_CONNECT_SQL_REPLACE.syn ）如下所示：

__DEF_FUZZY__             Y
__DEF_DEBUG__             N
__DEF_CASE_SENSITIVE__    N
 
__DEF_LINE_COMMENT__      -- 
__DEF_LINES_COMMENT__     /*     */
 
 
__DEF_STR__   __IF_KW__
<1,100>
[1,1]ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
[0,100]ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_
			  
 
__DEF_PATH__    __START_WITH_CONNECT__
1             : sel        @ %__IF_KW__            | select
              : cc         @                       | *
              : frm        @                       | from
              : srctab     @                       | __NAME__
              : sta        @ %__IF_KW__            | start
              : wth        @ %__IF_KW__            | with
              : swp        @                       | __NAME__
              : dy1        @                       | =
              : int        @                       | __INT__
              : str        @                       + __STRING__
              : cnn        @ %__IF_KW__            | connect
              : by         @ %__IF_KW__            | by
              : ncy        @ %__IF_KW__ CAN_SKIP   | nocycle
              : prr1       @ %__IF_KW__ CAN_SKIP   | prior
              : col1       @                       | __NAME__
              : dy         @                       | =
              : col2       @                       | __NAME__
              : end        @                       | ;
-----------------------------------------------------------------------
1             : sel        @                       | with
              : sel        @                       | recursive
              : sel        @                       | wr_
              : srctab     @                       \ __NAME__
              : sel        @ STRING                | as
              : sel        @                       | __\n__
              : sel        @                       | (
              : sel        @                       | __\n__
              : sel        @                       | select
              : col1       @                       / __NAME__
              : col2       @                       \ ,
              : col2       @                       / __NAME__
              : sel        @ STRING                \ , 1 as level from
              : srctab     @                       / __NAME__
              : sta        @                       / where
              : swp        @                       / __NAME__
              : dy1        @                       / =
              : int        @                       / __INT__
              : str        @                       / __STRING__
              : sel        @                       | __\n__
              : sel        @                       | union
              : sel        @                       | __\n__
              : sel        @                       | select
              : srctab     @                       / __NAME__
              : srctab     @                       \ .
              : col1       @                       \ __NAME__
              : col2       @                       \ ,
              : srctab     @                       / __NAME__
              : srctab     @                       \ .
              : col2       @                       \ __NAME__
              : sel        @ STRING                \ , level + 1 from
              : srctab     @                       / __NAME__
              : srctab     @                       \ ,
              : sel        @                       / wr_
              : srctab     @                       \ __NAME__
              : sta        @                       / where
              : srctab     @                       / __NAME__
              : srctab     @                       \ .
              : col2       @                       \ __NAME__
              : dy1        @                       / =
              : sel        @                       / wr_
              : srctab     @                       \ __NAME__
              : srctab     @                       \ .
              : col1       @                       \ __NAME__
              : sel        @                       | __\n__
              : sel        @ STRING                | )
              : sel        @                       | __\n__
              : sel        @                       | select
              : sel        @                       | *
              : sel        @ STRING                | from
              : sel        @                       | wr_
              : srctab     @                       \ __NAME__
              : sel        @                       / order
              : sel        @                       / by
              : col1       @                       / __NAME__
              : end        @                       | ;
 
 
__DEF_STR__   __NAME__
<1,100>
[1,1]ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_??
[0,100]ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_??
[NO] create insert update delete truncate drop merge table select inner left join on from where group order partition by having union all with as set between and or like in is not null case when then pivot lateral view 
 
 
__DEF_STR__   __INT__
<1,100>
[1,100]0123456789
 
 
__DEF_SUB_PATH__   __STRING__
1       : x1                  | '
        : x2                  | __ANY__
        : x3                  | '

# 执行方式： ZGLanguage -e STATR_WITH_CONNECT_SQL_REPLACE.syn -r start_with_connect.sql -o result.sql

源代码下载： https://gitee.com/zgl-20053779/zglanguage