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當查詢返回空結果時,不會打印標頭。有沒有辦法在任何情況下強制打印標題?即使結果集爲空,SQLite也會強制打印標頭
例如,在這種情況下,結果不空.headers
編譯確實打印到.output
文件,但在查詢返回空結果的情況下該文件是空的(無頭)。我仍然希望在空角落的情況下將文件頭打印到文件中,因爲生成的輸出文件適用於其他系統,並且依賴於這些頭文件。是否有可能在結果文件中強制標題?
-- setup to provide headers and to output as csv
.headers on
.mode csv
-- Attaching the databases
attach '/tmp/1.db' as existingdb;
attach '/tmp/2.db' as newdb;
-- Deletions query
.output /tmp/test/res/deletes.csv
SELECT a.sku AS "old:sku" , a.c1 AS "old:c1" , a.c2 AS "old:c2" FROM existingdb.products AS a LEFT JOIN newdb.products AS b on a.sku = b.sku WHERE b.sku IS NULL;
另一個簡單的例子:
sqlite> .tables
sqlite> create table test(a,b,c);
sqlite> select * from test;
sqlite>
sqlite> insert into test values (1,2,3);
sqlite> select * from test;
1|2|3
sqlite> .headers on
sqlite> select * from test;
a|b|c <<< the headers are printed
1|2|3
sqlite> select * from test where a = 2;
sqlite> result is empy - no headers are printed!
sqlite!= MySQL – Barmar