2. Like Operator-1
SELECT * FROM
[EMPLOYEE]
WHERE Name LIKE ‘D%'
SELECT * FROM
[EMPLOYEE]
WHERE Name LIKE ‘%D'
3.
4.
5. Like Operator-2
_dv.test.Where(x=> x.Name.ToString().Contains("1"));
SELECT [t0].[SN], [t0].[aaa]
FROM [test] AS [t0]
WHERE (CONVERT(NVarChar,[t0].[aaa])) LIKE @p0
_dc.test.Where(x=> x.Name.ToString().Equals("1"));
SELECT [t0].[SN], [t0].[aaa]
FROM [test] AS [t0]
WHERE (CONVERT(NVarChar,[t0].[aaa])) = @p0
8. OR Operator
SELECT * FROM Orders
WHERE
CustomerID='VINET'
OR
Freight=32.3800
SELECT * FROM Orders
WHERE
CustomerID='VINET'
UNION
SELECT * FROM Orders
WHERE Freight=32.3800
9. 子查詢(Subquery)
「獨立子查詢」
(Uncorrelated Subquery)
SELECT Name, Description
FROM Products
WHERE Quantity < 2 *
(
SELECT AVG( Quantity )
FROM Sales
);
「關聯子查詢」
(Correlated Subquery)
SELECT Name, Description
FROM Products
WHERE Quantity < 2 *
(
SELECT AVG( Quantity )
FROM Sales
WHERE Products.ID=Sales.ProductID
);
10. OUTER JOIN & NOT IN
SELECT E.ID
FROM Employee E
WHERE E.ID
NOT IN
(Select ID From SalaryAdj)
SELECT E.ID
FROM Employee E
LEFT JOIN SalaryAdj S
ON E.ID = S.ID
WHERE S.ID IS NULL
11. Join Table
SELECT a.id
FROM lxw1234_a a
left outer join partitioned b
ON (a.id = b.url);
WHERE b.day = ‘2015-05-10′
SELECT a.id
FROM lxw1234_a a
left outer join partitioned b
ON (
a.id = b.url
AND b.day = ‘2015-05-10′
);
16. Column Allow NULL?
儘量避免在 where 子句中對欄位進行 null 值判斷,會使系統
放棄使用索引而進行全表掃瞄
select id from t where num is null
可以在num上設置預設值0,確保表中num列沒有null值,然後
這樣查詢:
select id from t where num = 0