Opensql quick learning

https://www.cnblogs.com/jiangzhengjun/p/4264698.html#_Toc410466920

SELECT , INSERT ,UPDATE , DELETE , MODIFY

SELECT SINGLE … INTO…WHERE/

INNER JOIN ,LEFT OUTER JION Usage restriction

ON  The following conditions are similar to WHERE The conditions are similar , But there are the following differences 

1. There must be ON Conditional statements , And multiple conditions can only be used AND Connect
2. In each conditional expression , One of the two operands must be from JOIN Right table
3. If it is LEFT OUTER JOIN, Then at least one of the two operands of a conditional expression comes from the left table , One hour comes from the right
4. Out of commission NOT,LIKE,IN（ But if it is INNER JOIN, be > , < , BETWEEN … AND , <> You can use ）
5. If it is LEFT OUTER JOIN , You can only use the equal sign operator ：（ = , EQ）
6. If it is LEFT OUTER JOIN , The same right table cannot appear in different LEFT OUTER JOIN Of ON In the conditional expression
7. LEFT OUTER JOIN All fields in the right table of cannot appear in WHERE in
8. If it is LEFT OUTER JOIN, In the same ON In a conditional statement , It can only be associated with the same left table .

A few cases

* Sales order data 
SELECT vbeln,bstnk,kunnr,kvgr2			(vbeln Is the sales order number ,bstnk Is the customer reference number ,kunnr Customer code ,kvgr2 For the brand )
		FROM vbak
		FOR ALL ENTRIES IN @gt_so_inf
		WHERE vbeln = @gt_so_inf_vbeln
		INTO TABLE @DATA(lt_vbak).
SORT lt_vbak BY vbeln.

among sort The meaning of sorting , think lt_vak With vbeln Default ascending sort for criteria

For all entries in When to use ？
answer ：
1. For not join Table of , Use for all entries in Statement concatenates tables in a database table field
for all entries in Similar to external connection , To avoid repeated database queries , Use a field in the inner table as a condition , Get data from database tables ,
If there is one, choose , It is equivalent to filtering data
2. Check whether the inner table is empty , If it is empty , All data will be obtained
3. Out of commission LIKE,BETWEEN and IN（ Because these operators are uncertain comparison operators （ Set the selection conditions within a range ））
FOR ALL ENTRIES IN The function of the statement is equivalent to juxtaposing all the selection condition blocks .

ABAP in FOR ALL ENTRIES IN How to use it
stay ABAP In development , Cannot be used for join Or you need to use SELECT Inner table of , We usually use for all entries in Statement concatenates the table with the inner table , Find the required data , for example ; With BSEG Take the aggregation table as an example , as follows ：

SELECT bseg~kunnr      bseg~lifnr    bseg~belnr   INTO  TABLE  itab_bseg  FROM  bseg  FOR ALL  ENTRIES IN itab_main
WHERE bukrs  in_bukrs and (belnr = itab_main-belnr AND hkont = itab_main-hkont).

because BSEG Unable to join BSIS do inner join So first of all BSIS Put the content in itab_main in , And then use FOR ALL ENTRIES IN To connect

OPENSQL Study

1.SELECT sentence
INTO The result of the statement is not saved to the inner table , When it's a field or structure , Finally, add ENDSELECT sentence , This statement is equivalent to LOOP Loop execution SELECT sentence , Every time you take out a piece of data , Just add it to the structure , Keep reading all qualified data .

*------------- Use structure

* The structure used , Therefore use SELECT    ENDSELECT  sentence 
DATA:	gs_zht6 TYPE STANDRAD TABLE OF ZHR_TRAIN_ZHT_1,
			gs_zht7 TYPE ZHR_TRAIN_ZHT_1.

			SELECT * INTO gs_zht7 FROM ZHR_TRAIN_ZHT_1
				WHERE name EQ ' Zhou 0'
				WRITE : /gs_zht7-sex,
							  /gs_zht7-te1.
			ENDSELECT.

*------------- Use the inner table

* The internal table is used to save all values at once , So there is no ENDSELECT.
DATA: gs_zht9	TYPE STANDARD TABLE OF  ZHR_TRAIN_ZHT_1,
			gs_zht8 	TYPE ZHR_TRAIN_ZHT_1.

			SELECT *  INTO  TABLE gs_zht9 FROM ZHR_TRAIN_ZHT_1
				WHERE name EQ ' Zhou 0'.
			
			LOOP AT gs_zht9 INTO gs_zht8.
			WRITE:	/gs_zht8-tel,
							/gs_zht8-sex.
			ENDLOOP.