left-join

问题 I have three tables, machines holding vending machines, products holding all possible products, and machines_products which is the intersection of the two, giving how many of each product line is stocked in a particular machine. If a product is not stocked in a machine, there is no corresponding row in the third table. DESCRIBE machines_products; +------------+------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +------------+------------------+--

问题 I have three tables, machines holding vending machines, products holding all possible products, and machines_products which is the intersection of the two, giving how many of each product line is stocked in a particular machine. If a product is not stocked in a machine, there is no corresponding row in the third table. DESCRIBE machines_products; +------------+------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +------------+------------------+--

问题 I have below referenced query which groups studies counts by teacher, study year-month, and room for the past 12 months (including current month). The result I get is correct, however, I would like to include rows with zero counts for when the data is missing. I looked at several other related posts but could not get desired output: Postgres - how to return rows with 0 count for missing data? Postgresql group month wise with missing values Best way to count records by arbitrary time intervals

问题 SELECT A.CODE, B.NOTE, C.NUMBER FROM (A LEFT JOIN B ON A.CODE = B.CODE LEFT JOIN C ON A.CODE = C.NUMBER ) WHERE C.ID = B.ID Need to show some results combined from 3 tables, but my results show all data from table B reported also if the data isn't real from table C. Table A.code 1 2 3 Table B.code 1 2 3 Table B.note pippo paperino pluto Table C.number 1 Ideally there should be one result showing 1 1 pippo but in results it is shown: 1 1 pippo 1 1 paperino 1 1 pluto How can I get the real data

问题 I have three tables (SQLFiddle with tables created) Orange text is what I need to get by comparing Products.name with Filters.filter. I figured out that substring match can be done like this: on Products.name LIKE CONCAT('%',Filters.filter,'%'); I only need the first filter match to be used. So "Mushroom soup" will match "Soup" and not "Mushroom". What is best approach for this task? A tested SQLFiddle link, if possible, please. What I tried: ( feel free to skip everything below ) Tried

问题 I have the following database structure table_1 text_1 (INT) text_2 (INT) i18n id_i18n (PK INT) locale (PK VARCHAR(5)) text (TEXT) On table_1, the columns text_1 and text_2 are foreign keys pointing to some i18n.id_i18n entries. I can easily join the entries for a specific locale SELECT t1.text as text_1, t2.text as text_2 FROM table_1 LEFT JOIN i18n as t1 ON text_1 = t1.id_i18n and t1.locale = "en_us" LEFT JOIN i18n as t2 ON text_2 = t2.id_i18n and t2.locale = "en_us" I can also get the

问题 I need to join tableA to tableB on employee_id and the cal_date from table A need to be between date start and date end from table B. I ran below query and received below error message, Would you please help me to correct and query. Thank you for you help! Both left and right aliases encountered in JOIN 'date_start' . select a.*, b.skill_group from tableA a left join tableB b on a.employee_id= b.employee_id and a.cal_date >= b.date_start and a.cal_date <= b.date_end 回答1: RTFM - quoting

问题 I have a dataset I'm doing analysis on. It turns out it can easily be enriched with demographic and community data which vastly improves the analytical results. In order to do this I'm joining in demographic and community data before doing analysis. I need to exclude some fields from my core sample set, so my join looks something like this: select sampledata.c1, sampledata.c2, demographics.*, community.* from sample data join demographics using (zip) join community using (fips) This gets me

问题 I need to do a SELECT in 8 tables, but the results in not what I have expected. The ugly code: SELECT equipment.* FROM equipment LEFT JOIN equip_adaptador a ON (a.cod_equip = equipment.cod_equip) LEFT JOIN equip_antena aa ON (aa.cod_equip = equipment.cod_equip) LEFT JOIN equip_cable c ON (c.cod_equip = equipment.cod_equip) LEFT JOIN equip_conector cc ON (cc.cod_equip = equipment.cod_equip) LEFT JOIN equip_fonte f ON (f.cod_equip = equipment.cod_equip) LEFT JOIN equip_router r ON (r.cod_equip

问题 Context I'm trying to merge two big CSV files together. Problem Let's say I've one Pandas DataFrame like the following... EntityNum foo ... ------------------------ 1001.01 100 1002.02 50 1003.03 200 And another one like this... EntityNum a_col b_col ----------------------------------- 1001.01 alice 7 1002.02 bob 8 1003.03 777 9 I'd like to join them like this: EntityNum foo a_col ---------------------------- 1001.01 100 alice 1002.02 50 bob 1003.03 200 777 So Keep in mind, I don't want b_col