sql left join with where clause

Tags: style data sp on c R EF Size sql1, in TableA and TableB query TableA all data and TableB in TableA dataSELECT * FROM TableA A left join TableB B on A.key=b.key2, in the TableA query to exclude TableB data, the remaining TableA in the dataSELECT * FROM TableA A left join TableB B in A.key=b.key where B.key is null

You can use the into syntax and the defaultifempty () method to load null values in the right table. Example: VaR query = From R in db. Roles Join Sr in ( From SS in db. staffinroles Where ss. staffid = staffid Select SS ) On R. ID equals Sr. roleid Into X From y in X. defaultifempty () Select New roleinfo { Roleid = R. ID, Rolename = R. Name, Isset = y! = NULL }; Note that you can use y at the end! = NULL to determine whether the ri

Query the username, psw, gname, and tel of all realnames today.Table Structure:Table t1Field name: t1_id, username, pswTable t2Field name: t2_id, gname, t1_id // here one t1_id corresponds to multiple t2_idT3Field name: t3_id, realname, tel, t1_id // here, a t1_id corresponds to a t3_idThe trouble is that when a realname has no content in Table t2, the username, psw, and tel of this realname should be displayed and used directly.SQL = "select username, psw, gname, tel from t1, t2, t3 where t1.t1

1. Problem Introduction The main purpose is to query the data that appears in one table and not in the other, specifically: As shown, there is a, b two tables, where the aid field of Table B refers to the primary key ID of Table A, in order to query in a table appears, but not by the data referenced by B table; Qualification: The is_deleted field in A and B is ' n ' and the type in B is ' common '. 2. Workaround 2.1 Left

there is no corresponding data in the right to use NULL instead!3: Fully connected full join or complete outer JOIN, for the data in two tables come out, here to show the same effect!4: INNER JOIN inner JOIN or join; it is a record that returns a field ID that exists in bot

Kneeling for a LEFT JOIN SQL statement notation

the underlying SQL execution order SQL statements are executed in a certain order. Understanding this order is a great help in using and learning SQL. 1.from First select a table, or source, to form a result set. 2.where Then use where to filter the result set. Filter out the information needed to form a new result set. 3.group by Group the new re

null. The following table showsExternal join(Outer Join) retained data rows during Matching: Join type Retain data rows A left Outer Join B All a rows A right Outer Join B All B rows A

performance analysisUse tsql2012goset STATISTICS IO ONSET STATISTICS time ONSELECT l.id, L.valuefrom [Compare].t_left lleft JOIN [compare].t_right rON = l.valuewhere r.value is NULLHere we know it is clear that the result set is certainly the same, but the query plan and the above not EXISTS, does not have a big difference, left JOIN ... Is nul

SQL left JOIN keywordLeftjoin keyword will be from the left table (table_name1) where all the rows are returned, even in the right table (table_name2) There are no matching rows in the. Left JOIN keyword SyntaxSELECT column_name

Tags: strong div c SQL 404 romThe LEFT join returns records that include all records in the left table and the equivalent of the junction fields in the right table;Right join returns records that include all records in the right table and the junction fields in the

SQL left JOIN keywordThe left JOIN keyword returns all rows from the table (TABLE_NAME1), even if there are no matching rows in the right table (table_name2).Left JOIN keyword syntaxSEL

Label:We know that lambda expressions use the Join function in LINQ to SQL and the Entity framework to implement inner joins, so how can you implement a LEFT join in a lambda expression? The trick is to add a function DefaultIfEmpty function to the join, and in fact this fun

The SQL statements are as follows:SELECT *From table 1Left JOIN table 2 on table 1.id = Table 2.id and table 2. Name! = ' ff 'WHERE table 1.NAME! = ' AA 'Step 1: Return to Cartesian product (SELECT * from table 1 cross JOIN table 2)Step 2: Apply the on filter (the current condition is table 1.id = Table 2.id and table 2. Name! = ' ff ')Step 3: Add an external row

SQL Join left federated Associated Query instance tutorial Table A: Results and data StudentID WorkID Store1 1 981 2 952 1 902 3 80 Table B: Results and dataWorkID Workname1 Zuoye2 www.111cn.net3 Wenti We're going to use join left federated query results for the followin

Today I want to check all the Realname Username,psw,gname,tel Table structure: Table T1 Field Name: T1_ID,USERNAME,PSW Table T2 Field Name: t2_id,gname,t1_id//Here a t1_id corresponds to multiple t2_id T3 Field Name: t3_id,realname,tel,t1_id//Here a t1_id corresponds to a t3_id The trouble is when a realname in the T2 table does not have content, but also to the Username,psw,tel of this realname display, direct use Sql= "Select Username,psw,gname,tel

(). iterator (). Next (); Another important thing to know are that you can only fetch one collection reference in a query. That means you can just the use one fetch join. Can however fetch "one" references in addition, as this sample from the Hibernate Docs demonstrates: From eg. Cat as Cat INNER JOIN Fetch Cat.mate Left JOI