feat:修复问题#68,增加按cond拼接等

[bingtianyiyan]

1.增加按条件判断拼接查询
2.修复SelectCount对查询有设置Select并且数量只有一个且有设置别名,生成sql不对问题
3.增加Tx事务

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[afumu]

@bingtianyiyan
在下面回复一下这个哈，这样ci才能通过

[bingtianyiyan]

I have read the CLA Document and I hereby sign the CLA