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Add note about SELECT CAST(MeN AS CHAR) incompatibility #7663

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merged 7 commits into from
May 15, 2023
Merged

Add note about SELECT CAST(MeN AS CHAR) incompatibility #7663

merged 7 commits into from
May 15, 2023

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xuyifangreeneyes
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@xuyifangreeneyes xuyifangreeneyes commented Nov 24, 2021 •
edited by qiancai
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What is changed, added or deleted? (Required)

Add note about the incompatibility result of SELECT CAST(MeN AS CHAR) between TiDB and MySQL.

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Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions (in Chinese).

  • master (the latest development version)
  • v5.3 (TiDB 5.3 versions)
  • v5.2 (TiDB 5.2 versions)
  • v5.1 (TiDB 5.1 versions)
  • v5.0 (TiDB 5.0 versions)
  • v4.0 (TiDB 4.0 versions)
  • v3.1 (TiDB 3.1 versions)
  • v3.0 (TiDB 3.0 versions)
  • v2.1 (TiDB 2.1 versions)

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ti-chi-bot commented Nov 24, 2021 •
edited by ti-chi-bot bot
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[REVIEW NOTIFICATION]

This pull request has been approved by:

  • lilin90
  • qiancai

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@ti-chi-bot ti-chi-bot added missing-translation-status This PR does not have translation status info. size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Nov 24, 2021
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/cc @XuHuaiyu

XuHuaiyu
XuHuaiyu reviewed Nov 24, 2021
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data-type-numeric.md Outdated
@@ -163,6 +163,10 @@ DOUBLE PRECISION [(M,D)] [UNSIGNED] [ZEROFILL], REAL[(M,D)] [UNSIGNED] [ZEROFILL
>
> 与在 MySQL 中一样，`DOUBLE` 数据类型存储近似值。对于货币之类的精确值，建议使用 `DECIMAL` 类型。

> **注意：**
>
> TiDB 和 MySQL 在 `SELECT CAST(MeN AS CHAR)`（或者等价的 `SELECT CONVERT(MeM, CHAR)`）的结果显示上存在不一致，其中 `MeN` 是用科学计数法表示的双精度浮点数。MySQL 在 `N` 属于 `[-15, 14]` 范围时显示完整数值，在该范围外显示科学计数法。而 TiDB 始终显示完整数值。例如，MySQL 对于 `SELECT CAST(3.1415e15 AS CHAR)` 显示结果为 `3.1415e15`，而 TiDB 的显示结果为 `3141500000000000`。
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这里无需提到 cast 和 convert
只需要单纯的举例 select MeN，就已经不一样了

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我在 master 上试了一下，单纯 select MeN 是一致的，TiDB 也是 [-15, 14] 显示完整数值，否则科学计数法。

@TomShawn TomShawn self-assigned this Nov 24, 2021
@TomShawn TomShawn added area/sql-infra Indicates that the Issue or PR belongs to the area of sql-infra and sql-metadata. translation/doing This PR’s assignee is translating this PR. type/enhancement The issue or PR belongs to an enhancement. and removed missing-translation-status This PR does not have translation status info. labels Nov 24, 2021
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@xuyifangreeneyes 只适用于 master，不适用于 v5.3 吗？

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@xuyifangreeneyes 只适用于 master，不适用于 v5.3 吗？

4.0, 5.0, 5.1, 5.2, 5.3 都有这个不一致的行为，所以都要 cherry-pick?

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TomShawn commented Dec 2, 2021

@xuyifangreeneyes 只适用于 master，不适用于 v5.3 吗？

4.0, 5.0, 5.1, 5.2, 5.3 都有这个不一致的行为，所以都要 cherry-pick?

如果只是补充说明优化文档，建议就改 master。

@TomShawn TomShawn added the status/PTAL This PR is ready for reviewing. label Dec 6, 2021
@TomShawn TomShawn added the needs-cherry-pick-release-6.5 Should cherry pick this PR to release-6.5 branch. label Dec 28, 2022
lilin90
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qiancai commented Apr 6, 2023

Removed the needs-cherry-pick-release-6.3 label because the v6.3 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v6.3 and will no longer receive new updates.

@ti-chi-bot ti-chi-bot bot added status/LGT2 Indicates that a PR has LGTM 2. and removed status/LGT1 Indicates that a PR has LGTM 1. labels May 10, 2023
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@qiancai qiancai added translation/done This PR has been translated from English into Chinese and updated to pingcap/docs-cn in a PR. and removed translation/doing This PR’s assignee is translating this PR. status/PTAL This PR is ready for reviewing. labels May 10, 2023
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qiancai commented May 15, 2023

/merge

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This pull request has been accepted and is ready to merge.

Commit hash: aa829a7

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In response to a cherrypick label: new pull request created to branch release-6.5: #13964.

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In response to a cherrypick label: new pull request created to branch release-6.6: #13965.

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In response to a cherrypick label: new pull request created to branch release-7.0: #13966.

This was referenced May 15, 2023
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Add note about SELECT CAST(MeN AS CHAR) incompatibility (#7663) (#13965)
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ti-chi-bot bot pushed a commit that referenced this pull request May 15, 2023
@ti-chi-bot
Add note about SELECT CAST(MeN AS CHAR) incompatibility (#7663) (#13966)
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ti-chi-bot bot pushed a commit that referenced this pull request May 15, 2023
@ti-chi-bot
Add note about SELECT CAST(MeN AS CHAR) incompatibility (#7663) (#13964)
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@qiancai qiancai qiancai approved these changes

@lilin90 lilin90 lilin90 approved these changes

@XuHuaiyu XuHuaiyu XuHuaiyu approved these changes

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