Your second date is before your first date (ie. you are querying between September 29 2010 and January 30 2010). Try reversing the order of the dates: SELECT * FROM `objects` WHERE (date_field BETWEEN ‘2010-01-30 14:15:55’ AND ‘2010-09-29 10:15:55’)
You should use IS NOT NULL. (The comparison operators = and <> both give UNKNOWN with NULL on either side of the expression.) SELECT * FROM table WHERE YourColumn IS NOT NULL; Just for completeness I’ll mention that in MySQL you can also negate the null safe equality operator but this is not standard SQL. … Read more
Not only is the boolean datatype missing in Oracle’s SQL (not PL/SQL), but they also have no clear recommendation about what to use instead. See this thread on asktom. From recommending CHAR(1) ‘Y”https://stackoverflow.com/”N’ they switch to NUMBER(1) 0/1 when someone points out that ‘Y”https://stackoverflow.com/”N’ depends on the English language, while e.g. German programmers might use … Read more
Oh, I just found that command on PostgreSQL forum: SELECT * FROM pg_stat_activity;
If you are using SQL Server 2005+, then you can use the PIVOT function to transform the data from rows into columns. It sounds like you will need to use dynamic sql if the weeks are unknown but it is easier to see the correct code using a hard-coded version initially. First up, here are … Read more
Quote, which summarizes from this article: SET is the ANSI standard for variable assignment, SELECT is not. SET can only assign one variable at a time, SELECT can make multiple assignments at once. If assigning from a query, SET can only assign a scalar value. If the query returns multiple values/rows then SET will raise … Read more
The MERGE statement merges data between two tables. Using DUAL allows us to use this command. Note that this is not protected against concurrent access. create or replace procedure ups(xa number) as begin merge into mergetest m using dual on (a = xa) when not matched then insert (a,b) values (xa,1) when matched then update … Read more
There is no ranking functionality in MySQL. The closest you can get is to use a variable: SELECT t.*, @rownum := @rownum + 1 AS rank FROM YOUR_TABLE t, (SELECT @rownum := 0) r so how would that work in my case? I’d need two variables, one for each of col1 and col2? Col2 would … Read more
Since 9.0 this is even easier: SELECT id, string_agg(some_column, ‘,’) FROM the_table GROUP BY id
DESCRIBE <table>; This is acutally a shortcut for: SHOW COLUMNS FROM <table>; In any case, there are three possible values for the “Key” attribute: PRI UNI MUL The meaning of PRI and UNI are quite clear: PRI => primary key UNI => unique key The third possibility, MUL, (which you asked about) is basically an … Read more