How do I join based on conditions?

How do I join based on conditions?

2 Answers. DECLARE @SQL NVARCHAR(MAX); SELECT @SQL = N’SELECT * FROM T1 INNER JOIN ‘ + CASE WHEN @Parameter IS NULL THEN N’T2 t’ ELSE N’T3 t’ END + N’ ON T1.ID = t.ID’; EXEC sp_executesql @SQL; 3: UNION ALL and subquery.

How do I join two tables in SQL with conditions?

Different Types of SQL JOINs

1. (INNER) JOIN : Returns records that have matching values in both tables.
2. LEFT (OUTER) JOIN : Returns all records from the left table, and the matched records from the right table.
3. RIGHT (OUTER) JOIN : Returns all records from the right table, and the matched records from the left table.

Can we use case in join condition?

A conditional column join is a fancy way to let us join to a single column and to two (or more) columns in a single query. We can accomplish this by using a case statement in the on clause of our join. A case statement allows us to test multiple conditions (like an if/else if/else) to produce a single value.

What happens when you join two tables without any condition?

One way to join two tables without a common column is to use an obsolete syntax for joining tables. The query will return a Cartesian product (a cross join), whose result set has the total number of rows equal to the number of rows in the first table multiplied by the number of rows in the second table.

Why do you need to know which table to join?

Note: Because the Unioned tables have scalar constants in the first field, and because that field is used in the join, the optimiser is able (depending on the RDBMS) to avoid attempting to redundantly join on both tables. (Enough information is present to ‘know’ which table to join on.)

How to join different tables depending on column value?

So, if in P.type is ‘C’ it represents a table named C, if the value is ‘D’ it represents a table named D. Now I want to have a SELECT statement which gives me values from table C or D respectively, depending on P.type.

When to use two left join s in SQL?

(Enough information is present to ‘know’ which table to join on.) If the two tables vary significantly enough to make the UNION ALL impractical, then using two LEFT JOIN s may be you best option.

Can you join more than one table in Sind?

Sind it is possible that the number of possible tables to join can extend (the values of p.type may increase from C and D to E, F, G.) I’d prefer to only join the ONE table specified by p.type rather that using a UNION above all possible tables.